ENGINEERING  LIBRARY 


INTERNATIONAL   CHEMICAL  SERIES 
H.  P.  TALBOT,  PH.D.,  Sc.D.,  CONSULTING  EDITOR 


TECHNICAL 
GAS  AND  FUEL  ANALYSIS 


Engineering 
Library 


COPYRIGHT,  1913,  1920,  BY  THE 
MCGRAW-HILL  BOOK  COMPANY,  INC. 


PRINTED  IN   THE   UNITED   STATES   OF   AMERICA 

f 


THE  MAPUE  PRES9  •  YORK  PA 


PREFACE  TO  SECOND  EDITION 

The  years  intervening  since  the  appearance  of  the  first  edition 
have  seen  a  distinct  increase  in  our  knowledge  of  the  subjects 
covered  in  this  book.  Standard  Methods  for  Sampling  and 
Analysis  of  Coal  and  Coke  and  also  for  Examination  of  Liquid 
Fuels  have  been  studied  and  approved  by  several  technical 
societies.  Methods  for  analysis  of  gases  have  been  critically 
studied  and  new  technique  developed  by  the  staffs  of  various 
organizations,  notably  the  Bureau  of  Mines  and  the  Bureau  of 
Standards,  and  by  a  number  of  individual  workers.  The  litera- 
ture has  been  carefully  reviewed  for  this  edition  and  the  inclusion 
of  new  material  has  increased  the  size  of  the  book  about  twenty 
per  cent.  No  attempt  has  been  made  to  describe  all  of  the  new 
methods  nor  to  illustrate  all  of  the  various  forms  of  apparatus 
now  on  the  market.  On  the  contrary  the  effort  has  been  to 
illustrate  types  and  to  indicate  essential  features.  Criticism 
has  been  solicited  from  teachers  who  have  used  the  book  as  a 
text  and  the  needs  of  students  have  been  kept  in  mind,  but  the 
intention  has  also  been  to  make  the  book  one  which  would 
supply  the  practicing  engineer  and  chemist  with  the  most 
necessary  information. 

ANN  ARBOR,  MICHIGAN, 
May,  1920. 


PREFACE  TO  FIRST  EDITION 

With  the  increased  demand  for  the  economic  utilization  of 
fuels  has  come  an  increased  necessity  for  accuracy  in  testing 
both  the  raw  fuel  and  the  manner  of  its  utilization.  Our  knowl- 
edge has  recently  been  greatly  extended  by  the  investigations 
conducted  by  the  Committee  on  Calorimetry  of  the  American 
Gas  Institute,  the  International  Photometric  Commission,  the 
Joint  Committee  on  Coal  Analysis  of  the  American  Chemical 
Society  and  the  Society  for  Testing  Materials,  the  Bureau  of 
Mines  and  the  Bureau  of  Standards. 

The  author  has  aimed  to  present  the  conclusions  of  these 
committees  and  also  to  indicate  where  there  has  been  marked 
dissent  from  them.  He  desires  to  express  his  especial  appre- 
ciation to  Professor  0.  L.  Kowalke  of  the  University  of  Wis- 
consin for  his  courtesy  in  revising  the  chapter  on  Determination 
of  Heating  Value  of  Gas;  to  Professor  S.  W.  Parr  of  the  Uni- 
versity of  Illinois  for  suggestions  on  Calorimetry  and  Chemical 
Analysis  of  Coal;  and  to  Dr.  H.  C.  Dickinson  of  the  Bureau  of 
Standards  for  his  suggestions  on  Calorimetry. 

ANN  ARBOR,  MICHIGAN, 
August,  1913. 


vii 


CONTENTS 

PAGE 
PREFACE    v 

CHAPTER  I 

SAMPLING  AND  STORAGE  OP  GASES    .    .    . % 

Difficulties  involved — The  problem  of  a  fair  sample — Materials 
for  sampling  tubes — Types  of  sampling  tubes  and  their  use — 
Aspirators — Solubility  of  gases  in  water — Saturating  water  in 
sampling  tanks — Collecting  an  average  sample  representative  of  a 
definite  period — Collecting  a  representative  instantaneous  sample 
— Storing  gas  samples. 

CHAPTER  II 

GENERAL  METHODS  OP  TECHNICAL  GAS  ANALYSIS 14 

introduction — General  method — The  gas  burette — Care  of  stop- 
cock— Saturating  the  water  of  the  burette — Drawing  the  sample 
of  gas  into  the  burette — Measuring  a  gas  volume — Calibration 
of  a  gas  burette — Gas  pipettes — Connecting  the  burette  and  pi- 
pette— Details  of  a  simple  gas  analysis — Accuracy  of  the  analysis. 

CHAPTER  III 

ABSORPTION  METHODS  FOR  CARBON  DIOXIDE,  UNSATURATED  HYDRO- 
CARBONS, OXYGEN,  CARBON  MONOXIDE  AND  HYDROGEN  ....  28 
Carbon  dioxide — Unsaturated  hydrocarbons — Oxygen  by  phos- 
phorus— Oxygen  by  alkaline  pyrogallate  or  hydrosulphite — Oxygen 
by  ammoniacal  copper  solution — Carbon  monoxide — Absorption  of 
hydrogen — General  scheme  of  analysis. 

CHAPTER  IV 

EXPLOSION  AND  COMBUSTION  METHODS  FOR  HYDROGEN,   METHANE, 

ETHANE  AND  CARBON  MONOXIDE 43 

Available  methods — Apparatus  for  explosion  analysis — Manipula- 
tion in  explosion  analysis — Oxidation  of  nitrogen  as  a  source  of 
error — Accuracy  of  explosion  methods — Hydrogen  by  explosion — 

ix 


X  CONTENTS 

PAGE 

Hydrogen  and  methane  by  explosion — Carbon  monoxide,  hydrogen 
and  methane  by  explosion — Quiet  combustion  of  a  mixture  of 
oxygen  and  combustible  gas — Fractional  combustion  with  palla- 
dinised  asbestos — Fractional  combustion  with  copper  oxide — 
Detection  of  minute  quantities  of  combustible  gas — Oxygen  by  ex- 
plosion or  combustion — Nitrogen — Form  of  record  of  gas  analysis. 

CHAPTER  V 

VARIOUS  TYPES  OP  APPARATUS  FOR  TECHNICAL  GAS  ANALYSIS.    .    .     £4 
Introduction — Schlosing  and  Holland's  apparatus — Orsat's  appa- 
ratus— Bunte's  burette — Chollar  tubes — Instruments  for  recording 
carbon  dioxide  in  flue  cases — Methods  of  gas  analysis  depending 
on  thermal  conductivity — Gas  analysis  by  optical  methods. 

CHAPTER  VI 

EXACT  GAS  ANALYSIS 74 

Historical — General  methods — Corrections  for  temperature  and 
pressure — Description  of  gas  burettes — The  bulbed  gas  burette 
for  exact  analj'sis — Manipulation  of  gas  burette  for  exact  analysis 
— Calibration  of  burette — Absorption  methods  in  exact  gas  analysis 
— Carbon  dioxide — Unsaturated  hydrocarbons — Oxygen — Carbon 
monoxide — Hydrogen — Methane — Errors  in  calculation  of  re- 
sults of  explosion  and  combustion — Nitrogen 

CHAPTER  VII 

HEATING  VALUE  OP  GAS ,    .    .    . 92 

Introduction — Continuous  flow  calorimeters — Wet  gas  meters — 
Corrections  for  temperature  and  pressure — Control  of  the  water — 
Measurement  of  temperature — Measurement  of  mass  of  water — 
Description  of  calorimeter — Preliminaries  of  a  test — Description 
of  a  test — Calculation  of  observed  heating  value — Total  heating 
value — Net  heating  value — Calculation  of  total  heating  value — Ac- 
curacy of  method — Determination  of  humidity  of  air — Non- 
continuous  water  heating  calorimeters — Automatic  and  recording 
gas  calorimeters — Calculation  of  heating  value  from  chemical 
composition. 

CHAPTER  VIII 

CANDLE-POWER  OF  ILLUMINATING  GAS      119 

Introduction — Method  of  rating  candle-power — The  bar  photo- 
meter— Standard  light — Photometric  units — Standard  candles — 


CONTENTS  xi 

PAGE 

The  Hefner  lamp— The  Pentane  lamp — Secondary  standards  of 
light — Standard  gas  burners — The  Bunsen  and  Leeson  photometric 
screens — The  Lummer  Brodhun  photometric  screen — The  flicker 
photometer — The  gas  meter — The  photometer  bench  and  its  equip- 
ment— Details  of  a  test — Illustration  of  calculation — The  photo- 
meter room — Jet  photometers — Accuracy  of  photometric  work. 

CHAPTER  IX 

ESTIMATION  OF  SUSPENDED  PARTICLES  IN  GAS 138 

Introduction — The  distribution  of  particles  in  the  cross-section  of 
a  straight  main — Mean  velocity  in  the  cross-section  of  a  gas  main — 
Influence  of  bends  in  a  main — Velocity  of  gas  in  a  sampling  tube — 
The  filtering  medium — Estimation  of  suspended  tar  and  water — 
Electrical  precipitation  of  suspended  particles 

CHAPTER  X 

CHIMNEY  GASES      144 

Introduction — Sampling — Formation  of  carbon  dioxide — Effect  of 
hydrogen  of  coal  on  composition  of  chimney  gases — Carbon  mono- 
xide and  products  of  incomplete  combustion — Volume  of  air  and  of 
chimney  gases — Loss  of  heat  in  chimney  gases — Interpretation  of 
analysis  of  chimney  gases. 

CHAPTER  XI 

PRODUCER  GAS 156 

Formation  of  producer  gas — Sampling  producer  gas — Analysis 
of  producer  gas — Interpretation  of  analysis — Heating  value  of 
producer  gas — Volume  of  producer  gas — Efficiency  of  a  gas 
producer. 

CHAPTER  XII 

ILLUMINATING  GAS  AND  NATURAL  GAS 163 

Introduction — Sampling — General  scheme  of  analysis — Chemical 
composition  of  illuminating  gas — Benzene — Benzene  and  light  oils 
by  differential  pressure  method — Hydrogen  sulphide — Total  sul- 
phur compounds — Naphthalene — Ammonia — Cyanogen — Specific 
gravity — Natural  gas — Gasoline  in  natural  gas. 

CHAPTER  Xlll 

LIQUID  FUELS  .    . 187 

Introduction — Sampling — Heating  value — Specific  gravity — Mois- 


xii  CONTENTS 

PAGE 

ture — Proximate  analysis — Suspended  solids — Flash  point — Gaso- 
line— Specifications  for  motor  gasoline — Kerosene — Fuel  oil. 

CHAPTER  XIV 

SAMPLING  COAL      204 

General  consideration — Difference  in  composition  of  lump  and  fine 
coal — A  scoopful  as  a  sample — Influence  of  lumps  of  slate-^- 
Taking  a  sample — Mine  sampling — Preparation  of  sample — Preser- 
vation of  sample — Usual  accuracy  of  sampling — Standard  methods 
of  sampling — Sampling  coke — Reliability  of  samples. 

CHAPTER  XV 

THE  CHEMICAL  ANALYSIS  OF  COAL 222 

Introduction — Proximate  analysis — Preliminary  examination  of 
sample — Air-drying — Grinding  and  preserving  the  sample  for 
analysis — Moisture — Volatile  matter — Ash — Fixed  carbon — Sul- 
phur— Ultimate  analysis — Carbon  and  hydrogen — Nitrogen — 
Phosphorus — Oxygen — Methods  of  reporting  analyses — Accuracy 
of  results — Slate  and  pyrites — Standard  methods  for  the  laboratory 
sampling  and  analysis  of  coal — Standard  methods  for  the  labora- 
tory sampling  and  analysis  of  coke. 

CHAPTER  XVI 

HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER 258 

General  methods  of  determining  heating  value — The  calorimetric 
bomb — Details  of  the  calorimetric  bomb — Thermometers — Prepa- 
ration of  sample — Manipulation  of  bomb  calorimeter — Thermom- 
eter corrections — Radiation  corrections — Corrections  for  oxida- 
tion of  nitrogen — Corrections  due  to  oxidation  of  sulphur — 
Correction  due  to  combustion  of  iron  wire — Reduction  to  constant 
pressure — Water  value  of  calorimeter — Adiabatic  calorimeter — 
Precision  calorimetry — Accuracy  of  results — Total  and  net  heating 
values. 

CHAPTER  XVII 

HEATING  VALUE  OF  COAL  BY  THE  PARR  CALORIMETER  AND  OTHER 

METHODS 282 

Introduction — Combustion  in  a  stream  of  oxygen — The  Thompson 
calorimeter — The  Parr  calorimeter — Preparation  of  Parr  calori- 
meter— Care  of  sodium  peroxide — Operation  of  Parr  calorimeter — 


CONTENTS  xiii 

PAGE 

Corrections  to  be  applied  with  Parr  calorimeter — Accuracy  of  Parr 
calorimeter — Calculation  of  heating  value  from  chemical  analysis. 

APPENDIX 290 

Saturation  pressure  of  water  vapor — Reduction  of  gas  volumes — 
Factors  for  reduction  of  gas  volumes — Relative  humidity — Correc- 
tions to  be  applied  to  observed  heating  values  of  illuminating  gas 
and  natural  gas — Emergent  stem  corrections  for  calorimeter  ther- 
mometers— Corrections  for  difference  between  inlet  water  tem- 
perature and  room  temperature  when  determining  heating  value 
of  gases — Table  for  constants  of  certain  gases  and  vapors — Mean 
specific  heats  of  gases — Volume  of  water  vapors  taken  up  by  one 
cubic  foot  of  air — Baume*  scale  for  liquids  lighter  than  water. 

INDEX .   305 


TECHNICAL 
GAS  AND  FUEL  ANALYSIS 

CHAPTER  I 
SAMPLING  AND  STORAGE  OF  GASES 

1.  Difficulties  Involved. — The  problem  of  obtaining  a  repre- 
sentative sample  of  a  gas  for  analysis  presents  in  many  cases 
more  difficulties  than  the  analysis  itself.     If  the  gas  flowing 
through  a  main  were  of  perfectly  uniform  composition  throughout 
its  cross-section  and  also  throughout  its  length  the  problem  would 
simplify  itself  to  the  introduction  of  a  tube  through  which  a  por- 
tion of  gas  might  be  removed  for  analysis.     The  proposition 
becomes  at  once  more  complicated  when  it  is  necessary  to  sample 
gases  which  have  not  passed  through  any  adequate  mixing  chamber 
and  which  usually  travel  through  the  main  or  flue  in  pulsations 
of  widely  varying  composition.     Ocular  evidence  of  this  condition 
is  afforded  by  a  glance  at  the  average  smoke  stack  with  its  pulsing 
billows  of  smoke.     If  it  is  desired  to  determine  not  only  the  com- 
position of  the  fixed  gases  but  also  the  amounts  of  suspended 
solids,  tar  particles,  water  globules,  etc.,  the  problem  becomes 
one  of  great  complexity,   capable   frequently  of    only  partial 
solution.     This  question  is  discussed  separately  in  Chapter  IX. 

2.  The  Problem  of  a  Fair  Sample. — Gases  should  be  sampled 
as  close  as  possible  to  the  point  of  the  reactions  which  are  to  be 
studied,  thus  minimizing  errors  due  to  leakage  of  air  or  gas, 
deposition  of  solids  or  secondary  reactions.     Gases  travel  through 
straight  pipes  in  an  irregular  succession  of  waves  of  rather  a 
spiral  form,  the  velocity  being  greatest  at  the  center  of  the  pipe 
and  least  next  to  the  walls.     The  shape  of  the  wave  is  altered  by 
every  bend,  branch  or  other  change  in  the  pipe  and  the  point  of 
maximum  velocity  is  also  shifted.     The  temperature  of  gases 
from  hot  furnaces  also  varies  throughout  the  cross-section  of  the 

1 


2  GA3  AND  FUEL  ANALYSIS 

conducting  pipe,  being  usually  hottest  where  the  velocity  is 
greatest  and  coldest  next  to  the  walls  and  in  dead  bends. 

It  is  in  general  advisable  to  sample  from  a  point  of  approxi- 
mately average  velocity  and  temperature,  but  it  is  not  possible  to 
find  a  single  point  from  which  a  truly  representative  instantaneous 
sample  can  be  drawn.  It  is  necessary  to  extend  the  sampling 
period  over  a  time  which  will  on  the  theory  of  probabilities  allow 
so  great  a  series  of  gas  waves  to  pass  the  sampling  tube  that  the 
resulting  sample  will  be  truly  representative.  A  small  volume  of 
gas  can  therefore  only  be  considered  a  representative  sample 
when  it  has  been  drawn  from  a  practically  homogeneous  mass  of 
gas — a  condition  which  is  rather  closely  fulfilled  in  illuminating 
gas  which  has  been  purified  and  further  made  uniform  through 
mixing  and  diffusion  in  a  large  gas  holder.  The  condition  is  not 
fulfilled  in  producer  or  chimney  gases. 

No  fixed  time  can  be  set  as  the  most  desirable  for  a  single  gas 
sample.  If  the  sample  is  being  taken  from  chimney  gases  which 
are  supposed  to  be  the  same  from  one  hour  to  another,  the  sam- 
pling process  may  very  well  extend  over  one  hour  or  six  hours. 
The  longer  the  period  the  more  nearly  will  the  sample  be  an 
average  one.  The  same  thing  holds  true  for  illuminating  gas 
coming  from  a  holder,  but  it  would  not  hold  true  for  producer  gas 
from  a  single  producer  nor  for  illuminating  gas  from  a  single  re- 
tort, for  these  gases  vary  continuously  in  composition,  each  fresh 
charge  of  coal  commencing  a  new  cycle.  When  dealing  with  gases 
of  this  sort  it  is  necessary  to  start  and  stop  the  sampling  with  refer- 
ence to  some  definite  point  in  the  cycle.  A  truly  proportional 
sample  of  a  constantly  varying  gas  cannot  be  obtained  without 
rather  elaborate  precautions. 

3.  Materials  for  Sampling  Tubes. — Sampling  tubes  must  be 
of  a  material  which  will  not  react  with  the  gases  and  change 
their  chemical  composition.  Iron,  and  in  general  metals,  cannot 
be  used  at  high  temperatures.  Iron  reacts  with  carbon  dioxide 
quite  rapidly  at  200°  C.,  producing  carbon  monoxide  and  oxide 
of  iron.  It  also  reacts  readily  with  oxygen.  An  oxidized  pipe 
will  react  with  hydrogen  causing  that  gas  to  disappear  as  water 
at  equally  low  temperatures.  Pipes  with  rough  surface  will 
induce  a  rapid  catalytic  decomposition  of  such  gases  as  ammonia 
and  some  of  the  less  stable  hydrocarbons  at  a  rather  low  red  heat. 


SAMPLING  AND  STORAGE  OF  GASES  3 

The  best  materials  for  sampling  tubes  are  glass,  quartz  or 
porcelain.  These  tubes  should  be  protected  by  a  wrapping  of 
asbestos  in  the  form  of  paper  or  twine  and  should  be  slipped  into 
an  iron  jacket  which  takes  the  strain  off  the  tube  and  prevents 
sudden  temperature  changes.  Glass  begins  to  soften  about 
600°  C.  or  1100°  F.  and  on  long  exposure  to  a  red  heat  devitrifies 
and  ultimately  cracks  spontaneously  on  cooling.  Porcelain  will 
stand  about  1000°  C.,  but  at  higher  temperatures  the  glaze  com- 
mences to  soften.  Unglazed  porcelain  will  stand  a  higher  tem- 
perature and  special  refractory  mixtures  may  be  obtained  which 
will  not  soften  at  1700°  C.,  but  such  tubes  are  apt  to  be  porous 
and  should  only  be  used  if  proved  to  be  free  from  leaks.  Fused 
quartz  is  in  some  respects  admirable  as  a  material  for  sampling 
tubes,  since  its  coefficient  of  expansion  is  so  small  that  it  never 
cracks  because  of  temperature  changes.  It  will  stand  1100°  C. 
without  softening  but  on  long  heating  tends  to  become  crystalline 
and  brittle.  The  ordinary  opaque  electroquartz  tubes  are  often 
porous  and  should  be  carefully  tested  for  leaks  before  they  are 
used. 

4.  Types  of  Sampling  Tubes  and  Their  Use. — The  simplest 
form  of  sampling  apparatus  consists  of  a  single  tube  through 
whose  open  end  the  gases  are  aspirated.  When  sampling  from 
a  large  flue  the  sampling  tube  is  sometimes  closed  at  the  end  and 
perforated  at  various  points  along  its  length  with  the  expectation 
that  gas  will  be  drawn  uniformly  through  the  holes  at  intervals 
across  the  flue.  A  device  of  this  sort  usually  fails  of  its  purpose 
and  is  often  less  efficient  than  a  single  tube.  If  the  perforations 
are  all  of  the  same  diameter  they  will  allow  the  same  amount  of 
gas  to  pass  through  only  in  case  the  suction  is  the  same  on 
each.  This  condition  can  be  attained  in  practice  only  by 
making  the  perforations  small  and  the  suction  high  so  that  it 
will  be  practically  as  great  at  the  far  as  at  the  near  end  of  the 
sampling  tube.  But  such  small  holes  stop  quickly  with  dust  and 
are  not  practicable. 

A  better  device  to  secure  a  more  uniform  sample  from  the  gases 
of  a  flue  is  shown  in  Fig.  1.  It  consists  of  a  bundle  of  glass  tubes 
of  the  same  diameter  but  of  varying  lengths  which  are  wired  to- 
gether and  slipped  into  an  iron  pipe  not  quite  so  long  as  the  short- 
est glass  tube.  The  glass  tubes  are  cemented  into  this  with  neat 


4  GAS  AND  FUEL  ANALYSIS 

Portland  cement  in  such  a  manner  that  their  ends  next  the  threaded 
joint  are  all  even  and  about  2  in.  from  the  end  of  the  iron  tube. 
This  may  readily  be  accomplished  in  the  following  manner. 
Plug  the  threaded  end  of  the  iron  pipe  with  a  cork  and  stand  it 
vertically  on  the  corked  end.  Plug  one  end  of  each  of  the  glass 
tubes  with  putty  and  stand  them  in  the  iron  tube  with  their 
lower  ends  resting  on  the  cork.  Fill  the  iron  tube  for  3  in.  with 
a  paste  of  Portland  cement  and  water  and  allow  to  stand  for 
twelve  hours  to  harden.  The  sampler  is  finished  after  removing 
the  cork  and  putty  by  screwing  onto  the  iron  pipe  a  cap  which  is 
provided  with  a  1/4-in.  nipple  to  which  convenient  connection 
may  be  made.  The  suction  required  to  draw  a  slow  stream  of 
gas  through  a  smooth  tube  2  ft.  long  is  only  slightly  more  than 
that  required  for  a  1-ft.  tube.  The  empty  space  at  the  end 
of  the  pipe  acts  as  a  mixing  chamber  and  allows  a  fairly  satis- 
factory sample  to  be  drawn  through  the  nipple. 

The  sampling  tube  is  to  be  inserted  in  the  flue  in  such  a  way 


FIG.  1. — Multiple  gas  sampling  tube. 

that  there  will  be  no  leakage  around  it.  An  iron  gas  main  may 
be  drilled  and  tapped  to  receive  a  threaded  nipple  into  which 
the  sampling  tube  is  luted  when  in  use  and  which  is  closed  by  a 
cap  when  not  in  use.  When  a  hole  must  be  cut  through  a  brick 
wall  a  threaded  nipple  may  be  cemented  permanently  into  the 
wall  and  closed,  when  not  in  use,  with  a  cap.  If  only  a  single 
sampling  tube  is  used  it  should  be  inserted  to  about  the  point  of 
mean  velocity  of  the  gases,  a  subject  which  is  discussed  in  Chapter 
IX.  Where  a  multiple  sampling  tube  of  the  above  type  is  used 
it  should  be  inserted  so  that  the  longest  tube  reaches  at  least  to 
the  center  of  the  flue. 

It  is  frequent  but  bad  practice  to  connect  the  sampling  tube 
and  the  aspirator  by  a  rubber  tube.  Rubber  is  softened  and 
burned  by  hot  gases  and  yields  gaseous  products  which  contami- 
nate the  sample.  It  also  dissolves  tar  and  hydrocarbon  vapors 
and  even  permanent  gases  like  ethylene  in  sufficient  amount  to 
materially  change  the  character  of  the  gas.  Furthermore,  even 


SAMPLING  AND  STORAGE  OF  GASES  5 

the  best  rubber  is  never  gas  tight  but  always  allows  some  leakage. 
It  is  usually  necessary  to  use  a  small  amount  of  rubber  tubing 
in  making  connections,  but  its  use  should  be  restricted  to  lengths 
of  only  an  inch  or  two  where  it  serves  as  a  connector  between  glass 
or  metal  tubes.  When  thus  used  a  copper  wire  should  be  twisted 
tightly  around  the  rubber  where  it  slips  over  the  glass  tube  to 
ensure  a  tight  joint.  A  tightly  stretched  rubber  band  may  be 
used  instead  of  the  wire.  Small  lead  or  seamless  copper  tubes 
are  flexible  and  more  satisfactory  than  glass  where  the  tempera- 
ture is  not  so  high  that  the  gases  react  with  the  metal. 

5.  Aspirators. — The  commonest  form  of  aspirator  consists  of 
a  bottle  or  tank  initially  filled  with  water  which  flows  slowly 
out  and  is  replaced  by  the  gas.  With  this  form  of  aspirator  the 
suction  constantly  decreases  as  the  head  of  water  drops  and  there- 
fore the  flow  of  gas  slackens,  which  is  a  disadvantage.  This 
may  be  overcome  by  making  the  entering  gas  pass  down  through 
a  central  tube  and  then  bubble  up  through  the  water  on  the 
principle  of  the  Marriotte  bottle,  but  unless  the  water  of  the 
aspirator  has  been  previously  thoroughly  saturated  with  the  gas 
this  process  is  certain  to  change  the  composition  of  the  gas  very 
materially.  The  extent  of  the  error  introduced  by  failure  to 
observe  this  precaution  is  discussed  later.  A  film  of  heavy  par- 
affine  oil  is  sometimes  poured  on  the  water  of  the  aspirator 
bottle  to  prevent  interaction  between  the  water  and  the  gas. 
Such  an  oil-film  does  not,  however,  prevent  the  interaction  and 
does  not  even  make  it  much  slower.  If  oil  is  used  it  should  be  at 
least  as  heavy  as  a  lubricating  oil  so  that  it  will  not  give  off  any 
appreciable  volume  of  vapors  which  even  in  small  amount  will 
cause  difficulty  in  the  estimation  of  oxygen  by  phosphorus. 

011  should  not  be  used  when  the  gases  sampled  contain  hydro- 
carbons, since  these  are  quite  soluble  in  heavy  mineral  oils. 

Where  frequent  samples  are  to  be  drawn  a  pair  of  aspirator 
tanks  as  shown  in  Fig.  2  are  to  be  recommended.  Tanks  to  hold 
approximately  a  cubic  foot  should  have  the  cylindrical  portion 

12  in.  in  diameter  and  12  in.  high  with  the  cones  each  6  in.  high. 
They  may  be  made  of  galvanized  iron  and  will  be  strong  enough 
with  merely  soldered  seams  if  they  are  not  knocked  about  too 
much.     The  ends  of  the  cones  terminate  in  short  1/2-in.  nipples 
soldered  in.     The  lower  end  of  the  tank  carries  screwed  to  this 
nipple  a  1/2-in.  cock  F,  anc!  beyond  this  another  1/2-in.  nipple 


6  GAS  AND  FUEL  ANALYSIS 

with  a  hose  union.  The  upper  nipple  carries  a  1/2-in.  tee  on 
whose  side-arm  is  an  ordinary  1/4-in.  gas  cock  E,  and  on  whose 
upper  end  is  a  cap  tapped  for  a  1/4-in.  pipe.  This  pipe,  cut  the 
length  of  the  tank,  is  threaded  into  the  cap  from  the  inside  be- 
fore the  latter  is  in  place  so  that  when  screwed  together  the  1/4-in. 
pipe  runs  the  whole  length  of  the  tank  and  projects  through  the 
cap  enough  to  receive  the  gas  cock  D.  With  a  pair  of  bottles 
of  this  sort  the  water  flows  from  one  to  the  other  and  is  not 
exposed  to  the  air  so  that  it  remains  saturated  with  the  gas. 

If  a  water  or  steam  line  is  at  hand  an  injector  may  be  employed 
as  an  aspirator.  It  is  desirable  in  most  cases  to  have  the  suction 
a  slight  and  steady  one,  a  condition  not  readily  attained  with 
injectors  running  only  to  a  small  per  cent,  of  their  capacity.  It  is 
well  to  have  the  injector  open  more  widely  than  is  necessary  to 
furnish  the  suction  required  and  to  have  on  the  line  an  automatic 
water  seal  relief  valve  as  indicated  at  E  in  Fig.  3  which  will  suck 
in  air  at  the  inlet  of  the  aspirator  if  the  suction  rises  too  high. 

6.  Solubility  of  Gases  in  Water. — The  solubility  of  gases  in 
water  varies  with  the  temperature  and  the  pressure.  For  our 
treatment  it  will  be  sufficient  to  assume  that  the  gas  is  always 
under  atmospheric  pressure  and  at  ordinary  room  temperatures. 
Under  these  circumstances  the  solubility  of  the  common  gases  is 
as  follows: 


SOLUBILITY  OF  GASES  IN  WATER 

Expressed  as  the  volume  gas  dissolved  by  unit  volume  water  at  the  tem- 
perature of  the  experiment  when  in  contact  with  the  pure  gas  at  atmos- 
pheric pressure. 

— 1  770  ^ 


Carbon  dioxide                         

1.070 

0.826 

Oxvcen 

0.036 

0.031 

Nitrogen                              

0.019 

0.016 

Carbon  monoxide                               

0.027 

0.023 

Methane                           

0.039 

0.033 

Ethylene  

0.147 

0.119 

When  mixed  gases  are  in  contact  with  water  the  amount  of 
each  gas  dissolved  will  be  in  direct  proportion  to  its  volume  and 
its  solubility.  Thus  the  composition  of  pure  water  saturated 


SAMPLING  AND  STORAGE  OF  GASES 


Composition  of 
air,  per  cent. 

Volumes  of  gases  in  100  vols. 
water 

Percentage  com- 
position of  gas 
dissolved  by  water 

CO2  0.04 
O2  21.0 
N2  79.0 

0.04X1.07   =0.043  vols.  CO2 
21.0   XO.  036  =0.756  vols.     O2 
79.0   X  0.019  =  1.500  vols.     N2 

1.9 

32.9 
65.2 

Total  dissolved  gas  =2.299  vols. 


100.0 


The  composition  of  the  gases  in  water  saturated  with  chimney 
gases  may  be  calculated  in  the  same  manner. 


Composition  of 
gas,  per  cent. 

Volumes  of  gases  in  100  vols. 
water 

Percentage  com- 
position of  gas 
dissolved  by  water 

C02  
O2                  

10 
10 

10X1.07    =10.70 
10X0.036=  0  36 

85.0 
2.9 

N2 

so 

80X0  019=   1  52 

12.1 

12.58 

100.0 

The  change  in  the  carbon  dioxide  from  10  per  cent,  of  the  gas 
sampled  to  85  per  cent,  of  the  gases  dissolved  in  water  shows  how 
serious  are  the  errors  which  can  arise  in  sampling.  If  the  sam- 
pling tank  originally  filled  with  pure  water  should  be  only  half 
emptied  so  that  it  would  be  half  filled  with  gas  of  the  above 
composition  and  half  filled  with  water,  and  then  it  should  be 
allowed  to  stand  till  equilibrium  were  attained,  7  per  cent,  of  the 
gas  would  be  dissolved  by  the  water  with  the  following  result. 


Original  composition 
of  gas,  per  cent. 

Composition  gas  after 
standing  over  water, 
per  cent. 

Composition  of 
gases  dissolved  by 
water,  per  cent. 

CO2  10.0 

5.2 

73.4 

O2              .        .  .    10  0 

10  4 

5.0 

N,.                       ..80.0 

84.4 

21.6 

The  above  illustration  shows  that  in  chimney  gases  it  is  not 
at  all  impossible  to  have  an  error  of  50  per  cent,  hi  the  C(>2 
through  carelessness  in  sampling.  Errors  of  similar  nature,  al- 
though hardly  of  such  large  proportions,  will  arise  with  other  gases. 
With  illuminating  gas  it  is  the  important  class  of  illuminants  of 


8  GAS  AND  FUEL  ANALYSIS 

the  ethylene  series  which  is  most  seriously  affected.  If  it  is 
worth  while  taking  a  sample  at  all  it  is  worth  while  to  saturate 
the  water  with  which  the  gas  is  to  come  in  contact. 

7.  Saturating  Water  in  Sampling  Tanks. — When  the  gas  to  be 
sampled  is  under  pressure  it  may  be  bubbled  through  the  water 
contained  in  a  bottle,  best  only  about  two-thirds  full  of  water 
and  loosely  stoppered.     The  air  of  the  bottle  will  soon  be  replaced 
by  the  gas  which  will  thus  act  on  the  constantly  changing  surface 
of  the  liquid  as  well  as  on  the  surface  exposed  to  the  bubbles. 
An  occasional  vigorous  shake  will  greatly  accelerate  absorption. 
Under  these  conditions  the  water  will  become  practically  saturated 
in  fifteen  minutes.     It  is  not  wise  to  attempt  to  saturate  water 
by  bubbling  the  gas  through  it  while  in  an  open  beaker,  since  the 
constant  presence  of  the  air  above  the  liquid  defeats  the  very 
object  aimed  at. 

The  water  in  tanks  of  the  form  shown  in  Fig.  2  may  be  readily 
saturated  if  suction  is  available  by  connecting  tank  1  to  the  gas 
main  as  shown  and  connecting  the  suction  pipe  to  cock  E  of  the 
same  tank.  The  gases  will  then  bubble  through  the  water  and 
pass  out  E.  Where  suction  is  not  available  the  procedure  is  as 
follows.  Start  with  tank  1  full  of  water  and  tank  2  empty.  Fill 
tank  1  with  gas  and  connect  the  cocks  E  on  the  two  tanks  with 
rubber  tubing.  Raise  tank  2.  Water  will  flow  from  2  into  1 
and  gas  from  1  to  2.  When  each  is  approximately  half -full  close 
the  valves  and  shake.  Finish  passing  the  water  from  2  into  1  and 
disconnect  the  rubber  tube  from  E  of  tank  2.  Draw  a  fresh 
tankful  of  gas  into  1,  allowing  that  in  2  to  escape  into  the  air. 
Connect  the  cocks  E  with  rubber  tubes  as  before  and  repeat  the 
process  of  dividing  the  gas  and  water  between  the  two  tanks  and 
shaking.  After  three  such  operations  the  water  will  be  suffi- 
ciently saturated. 

8.  Collecting  an  Average  Sample  Representative  of  a  Definite 
Period. — -It  is  frequently  desirable  to   determine  the  average 
composition  of  gases  flowing  through  a  flue  for  a  period  of  time 
which  may  be  15  minutes  or  24  hours.     If  the  period  is  not 
longer  than  an  hour  the  use  of  two  cu.  ft.  tanks  as  shown  in  Fig.  2 
is  satisfactory,  it  being  assumed  that  only  the  true  gases  are  of 
importance  and  that  suspended  solids  and  condensable  vapors 
are  either  absent  or  unimportant.     A  represents  the  multiple 
sampling  tube  projecting  into  a  flue.     B  is  a  tube  loosely  packed 


SAMPLING  AND  STORAGE  OF  GASES 


9 


with  cotton  or  asbestos  to  filter  out  dust.  C  is  a  bubbling  tube 
to  indicate  the  rate  of  flow  of  the  gas.  The  first  step  in  a  test  is 
to  saturate  the  water  of  the  tanks  as  previously  directed.  At 
the  close  of  this  operation  tank  1  should  be  full  of  water  and  tank 
2  of  gas  and  the  sampling  tube  and  the  filter  should  be  full  of  gas. 
To  commence  the  sampling  operation  D  is  opened  fully  and  F  is 
opened  slightly  until  gas  bubbles  through  C  at  the  rate  desired. 
It  is  a  mistake  to  open  widely  the  lower  stopcock  on  the  sampling 
tank  and  control  the  flow  of  gas  by  partially  closing  the  upper 
stopcock,  since  with  this  procedure  the  gas  in  the  tank  is  under 


FIG.  2. — Apparatus  for  aspirating  a  sample  of  gas  from  a  flue. 

an  unnecessarily  reduced  pressure  and  there  is  an  unnecessary 
risk  of  leakage.  The  gas  in  tank  2  escapes  through  the  open 
cock  at  the  top.  The  pressure  gage  at  G  will  indicate  if  the 
sampling  tube  or  the  filter  becomes  choked.  The  rate  of  gas  flow 
should  be  so  adjusted  that  tank  1  will  be  almost  filled  with  gas 
at  the  end  of  the  period.  There  should  still  remain  enough 
water  to  act  as  a  stirrer  for  the  gas  when  the  tank  is  shaken 
vigorously  to  mix  the  contents.  This  mixing  is  a  simple  precau- 

L«  1     •       1  1  I  J  -I  «.    i  1  f,        •  ,  ,1  i  1 


10 


GAS  AND  FUEL  ANALYSIS 


mix  by  diffusion  but  the  rate  is  a  slow  one  and  it  is  never  safe  to 
rely  on  diffusion  to  give  a  fair  sample.  After  the  gas  in  tank  1 
is  mixed  a  portion  may  be  transferred  through  cock  E  to  a  labora- 
tory gas  holder  for  analysis.  To  get  ready  for  the  next  sample 
the  E  cocks  on  both  tanks  should  again  be  connected  by  the 
rubber  tube  and  the  gas  transferred  to  tank  2  so  that  the  water 
in  tank  2  will  remain  saturated. 

If  the  sampling  period  is  to  extend  for  much  more  than  an 
hour  the  flow  of  gas  through  the  sampling  tube  becomes  so  slow 
that  a  multiple  sampling  tube  is  not  to  be  relied  on.  The  use 
of  the  additional  apparatus  shown  in  Fig.  3  remedies  the  difficulty 
where  a  continuous  aspirator  is  available  to  draw  a  rapid  stream 
of  gas  through  the  sampling  tube.  The  gas  filter,  bubbling 
tube  and  sampling  tanks  of  Fig.  2  are  to  be  attached  to  cock  A 
of  Fig.  3.  The  sampling  tanks  may  then  be  set  to  take  as  slowly 


TuM 


FIG.  3. — Continuous  gas  sampling  apparatus. 

as  may  be  desired  a  portion  of  the  representative  rapidly  flowing 
gas  stream. 

In  Fig.  3,  B  is  a  pressure  gage  to  indicate  any  obstruction  of 
the  sampling  tubes,  C  is  a  bubbling  bottle  to  give  a  visual  control 
of  the  rate  of  the  stream,  D  is  a  gas  meter,  E  is  a  pressure  control 
and  F  a  pressure  gage  on  the  line  from  the  aspirator.  The  suc- 
tion on  the  sampling  tube  as  shown  by  gage  B  should  be  only  a 
few  tenths  of  an  inch  of  water.  It  is  difficult,  however,  to  get 
an  aspirator  to  work  properly  when  nearly  shut  off  so  that  the 
aspirator  is  opened  enough  to  work  efficiently  and  the  suction 
on  the  line  is  kept  down  by  the  regulator  E.  The  suction  on  B 
may  be  regulated  by  the  depth  to  which  the  tube  in  E  is  immersed. 
An  orifice  meter  may  be  substituted  for  the  dry  meter  shown  in 
the  installation  at  D.  Such  an  apparatus  may  be  made  of  metal 
or  may  be  made  quite  simply  from  glass  tubing.1 

1  Benton,  Jour.  Ind.  and  Eng.  Chem.,  xi,  623  (1919). 


SAMPLING  AND  STORAGE  OF  GASES  11 

The  title  of  this  section  calls  for  the  collection  of  a  sample 
representative  of  a  definite  period.  The  foregoing  procedure 
only  accomplishes  it  approximately.  In  order  that  the  sample 
should  be  truly  representative  a  given  proportion,  say  one-tenth 
of  1  per  cent,  of  the  gas,  should  be  constantly  passing  through  the 
sampling  tube.  If  the  flow  of  gas  in  the  main  dropped  to  one- 
third  of  its  former  rate,  the  flow  of  gas  through  the  sampling 
tube  and  into  the  sampling  tank  should  also  decrease.  The 
ideal  to  be  striven  for  is  to  have  in  the  small  sampling  tank  gas 
of  the  identical  composition  that  there  would  be  in  a  large  gas  holder 
where  all  of  the  main  gas  stream  had  been  gathered  and  mixed. 
This  can  only  be  accomplished  by  a  sampler  which  takes  repre- 
sentative quantities  as  well  as  qualities  of  gas.  The  sampling 
apparatus  described  is  supposed  to  work  at  a  constant  and  not  a 
proportionate  rate,  but  it  does  not  even  do  this  accurately. 
It  is  not,  however,  possible  to  take  a  truly  proportional  sample 
without  great  elaboration  of  equipment  and  the  method  described 
is  usually  sufficient. 

9.  Collecting  a  Representative  Instantaneous  Sample. — The 
problem  of  a  representative  instantaneous  sample  is  in  some  ways 
simpler  than  that  involved  in  collecting  a  sample  to  represent  a 
longer  period.     If  the  apparatus  shown  in  Fig.  3  is  attached  to  a 
multiple  sampling  tube  a  sample  drawn  at  A  should  be  fairly 
representative.     If  desired  an  Orsat  burette  or  similar  apparatus 
may  be  attached  permanently  at  A. 

10.  Storing  Gas  Samples. — Samples  of  gas  obtained  as  directed 
in  the  preceding  section  are  too  large  for  ready  transportation 
to  the  laboratory  for  analysis.     It  is  usually  convenient  to  trans- 
fer a  portion  to  a  small  glass  gas  holder  which  is  advantageously 
of  the  type  proposed  many  years  ago  by  Hempel  and  shown  in 
Fig.  4.     This  consists  of  a  bulb  terminated  above  by  the  gas 
inlet  of  capillary  tubing  bent  in  the  form  of  a  U  to  allow  a  water 
seal  and  at  the  bottom  by  a  larger  tube  for  the  water  supply. 
The  transfer  of  gas  is  accomplished  in  the  following  stages. 
Attach  at  cock  E  of  Figs.  2  and  4  a  glass  tee  carrying  at  A  a 
rubber  connection  and  a  small  funnel  and  at  B  a  rubber  con- 
nection.    Fill  the  gas  holder  with  water  taken  from  the  large 
sampling  tank  2  of  Fig.  2,  which  is  saturated  with  the  gas,  and 
connect  the  gas  holder  at  B  as  shown  in  Fig.  4,  with  the  exception 


12 


GAS  AND  FUEL  ANALYSIS 


of  the  screw  clamps  at  A  and  B.  Open  valve  E  and  blow  gas 
through  the  tee  and  out  A  to  expel  air.  Close  E  and  force  water 
from  the  small  gas  holder  into  the  funnel.  Tighten  clamp  A. 
Fill  the  glass  gas  holder  nearly  full  of  gas  and  close  E.  Open  A 
cautiously  and  allow  water  to  flow  from  the  funnel  and  fill  the 
capillary  seal  of  the  gas  holder.  Close  clamp  B  and  disconnect 
the  gas  holder  from  the  tee.  Elevate  the  levelling  bottle  so  as 
to  put  the  gas  in  the  holder  under  slight  pressure,  and  close  the 
clamp  C  at  the  bottom  of  the  holder.  The  gas  is  now  stored  in  a 


FIG.  4. — Glass  gas  holder  for  storing  samples. 


glass  vessel  closed  at  the  top  by  a  capillary  tube  filled  with  water, 
which  in  turn  is  closed  by  a  clamped  rubber  tube  at  the  top  of 
the  capillary.  At  the  bottom  the  holder  is  similarly  closed  by  a 
column  of  water.  The  gas  is  thus  in  contact  with  nothing  but 
glass  and  water  and  if  the  latter  has  been  previously  saturated, 


SAMPLING  AND  STORAGE  OF  GASES  13 

may  be  preserved  without  change  for  months.  The  above  form 
of  gas  holder  is  always  reliable.  The  galvanized  iron  sampling 
tanks  shown  in  Fig.  2  may  also  be  made  of  glass  on  a  smaller 
scale  and  used  for  storage  of  gases.  They  are  more  convenient 
where  samples  are  to  be  shipped  since  they  do  not  have  the  pro- 
jecting bent  capillary  which  is  liable  to  be  broken  in  shipment. 

Gas  holders  of  the  floating  type  are  not  to  be  relied  upon  for 
there  is  always  diffusion  of  gases  through  the  water,  and  after 
several  hours  evident  changes  may  be  found.  There  are  nu- 
merous forms  of  gas  holders  where  stopcocks  are  relied  upon  to 
prevent  leakage.  Stopcocks  may  be  tight  or  they  may  not  and 
anyone  who  has  had  experience  with  the  irritating  doubts  attend- 
ant upon  their  use  will  prefer  not  to  trust  them  more  than  is 
necessary.  The  same  thing  holds  true  of  rubber  stoppers  and 
connections.  Gases  may,  however,  be  transported  quite  safely 
in  glass  bottles  with  rubber  stoppers  provided  a  little  water  is 
left  in  the  bottle  and  the  stopper  is  wired  tightly  in  and  covered 
thickly  with  paraffine.  The  bottle  is  then  to  be  kept  upside  down. 
Under  these  conditions  the  small  amount  of  water  in  the  bottle 
forms  a  seal  on  the  inside  and  the  paraffine  a  seal  on  the  outside, 
re-enforcing  the  rubber.  When  samples  of  this  sort  are  to  be 
shipped  by  express  they  should  be  packed  in  crates  without  a  top 
so  that  care  will  always  be  taken  to  keep  the  proper  end  up. 
Where  gases  have  to  be  stored  a  long  time  and  especially  where 
they  must  be  shipped,  the  truly  safe  way  is  to  collect  them  in 
glass  tubes  drawn  out  at  each  end  and  fuse  the  ends  in  a  blowpipe 
flame. 


CHAPTER  II 
GENERAL  METHODS  OF  TECHNICAL  GAS  ANALYSIS 

1.  Introduction. — Gas  analysis  is  an  extremely  useful  method 
for  controlling  the  operation  and  checking  the  efficiency  of  many 
industrial  operations.  All  of  the  manifold  industries  using  fuel 
as  a  source  of  heat  and  almost  all  industries  engaged  in  producing 
fuel  or  utilizing  it  in  any  way  find  in  gas  analysis  a  valuable 
assistant.  There  are  very  many  special  industries  which  require 
the  analysis  of  gases  which  are  peculiar  to  themselves  and  not 
connected  with  fuels,  but  though  the  general  methods  of  gas 
analysis  here  given  will  often  apply  to  these  cases,  no  attempt 
will  be  made  to  develop  those  applications  which  might  better 
be  taken  up  in  connection  with  a  study  of  the  particular  indus- 
tries. This  chapter  will  consider  only  the  gases  arising  from  the 
utilization  of  fuels. 

The  purpose  for  which  the  analysis  is  desired  will  influence 
the  methods  to  be  employed  and  the  kind  of  apparatus  to  be 
used,  for  time  consumed  and  liability  to  errors  increase  rapidly 
with  the  number  of  constituents  to  be  determined.  The  analysis 
is  to  be  made  as  simply  as  possible,  small  percentages  of  gases 
unimportant  for  the  purpose  of  the  analysis  being  neglected  and 
groups  of  related  gases  being  frequently  determined  together. 
In  boiler  firing  and  in  the  operation  of  all  furnaces  heated  by 
combustion  of  fuel,  the  variations  in  the  percentages  of  carbon 
dioxide,  oxygen  and  carbon  monoxide  show  at  once  the  changes 
in  efficiency  of  the  furnace.  In  the  operation  of  gas  producers 
these  three  constituents  with  the  added  determination  of  hydro- 
carbons and  of  hydrogen  suffice  for  most  purposes.  When  gas 
is  to  be  sold  to  consumers,  as  is  the  case  with  a  city  gas  supply, 
a  more  complete  analysis  is  often  necessary  and  not  infrequently 
some  uncommon  and  minute  constituents  must  be  sought  as  an 
explanation  of  trouble. 

This  adaptation  of  the  means  to  the  end  is  a  characteristic  of 
technical  analysis,  which  seeks  only  the  particular  information 

14 


GENERAL  METHODS  OF  TECHNICAL  GAS  ANALYSIS      15 

of  value  for  the  purpose  in  hand.  On  this  account  gases  from 
different  sources  will  be  considered  separately,  although  there 
may  be  much  in  common  between  them.  There  are  various 
operations  common  to  almost  all  processes  of  gas  analysis  which 
may  well  be  considered  before  passing  to  special  cases,  and 
such  general  considerations  form  the  subject  of  this  chapter. 

2.  General    Method. — The   method    preferably    followed   in 
technical  gas  analysis  requires  a  measurement  of  the  initial 
volume  of  the  mixed  gas,  the  absorption  of  a  single  constituent 
by  an  appropriate  reagent,  and  the  measurement  of  the  new 
volume,  the  constituent  absorbed  being  determined  by  difference. 
Where  no  suitable  absorbent  is  known  for  a  given  constituent 
it  is  desirable  to  transform  the  gas  into  some  more  suitable 
compound.     It  is  necessary  in  order  that  these  changes  in  volume 
due  to  absorption  be  correctly  noted,  that  the  temperature  and 
pressure  of  the  gas  be  known  at  each  step,  and  it  would  be  ideal 
if  both  the  temperatures  and  pressures  could  be  kept  absolutely 
constant  throughout  the  process.     This  can  never  be  accom- 
plished, although  by  special  apparatus  described  in  Chapter  VI 
on  Exact  Gas  Analysis  errors  due  to  change  in  external  tem- 
perature and  pressure  during  an  analysis  may  be  automatically 
eliminated.     This    procedure    is,    however,    more    complicated 
than  is  necessary  for  technical  work  where  it  is  usually  suf- 
ficiently accurate  to  make  the  assumption  that  the  temperature 
of  a  water-jacketed  burette  in  a  laboratory  does  not  vary  during 
the  hour  that  may  be  required  for  an  analysis,  and  that  the 
barometric  pressure  does  not  change  in  the  same  period.     Since 
this  simpler  procedure  is  sufficiently  accurate  for  most  technical 
purposes,  it  will  be  described  first.     The  historical  development 
of  the  present  apparatus  and  methods  is  discussed  in  Chapter  VI 
on  Exact  Gas  Analysis. 

3.  The    Gas    Burette. — The  gas  burette  has  its  zero    point 
at  the  top  and  is  usually  of  100  c.c.  capacity.     It  is  closed  at  the 
top  by  a  stopcock  or  sometimes  simply  by  a  rubber  tube  and  a 
pinchcock  and  should  always  be  enclosed  in  a  water  jacket. 
Almost  all  forms  of  gas  burettes  will  answer  the  above  descrip- 
tion, but  there  are  many  differences  of  detail,  the  most  impor- 
tant being  the  style  of  the  stopcock  which  closes  the  burette  at 
the   top.    The  form  of  apparatus  which  has  been  evolved  in 


16 


GAS  AND  FUEL  ANALYSIS 


the  laboratory  of  the  University  of  Michigan1  and  which  has 
given  good  service  during  the  past  ten  years  is  shown  in  Fig.  5, 
which  illustrates  the  apparatus  as  it  appears  in  service. 
Details  are  given  in  Fig.  6.  The  burette-stand  may  be  im- 
provised from  an  ordinary  iron  stand,  one  of  whose  rings  of  ex- 
ternal diameter  slightly  greater  than  the  water  jacket  of  the 
burette  has  been  provided  with  a  brass  collar,  thus  making  a 


Rubber  Stopper 


100  c.c.  divided 
c.c. 


^  Rubber  Stopper 


FIG.  5. — Gas  burette  and 
pipette. 


FIG.  6.— Details  of  gas  burette. 


cup  in  which  the  rubber  stopper  of  the  water  jacket  rests  without 
binding.  Another  ring  large  enough  to  slip  loosely  over  the 
water  jacket  serves  to  keep  the  burette  vertical.  A  segment 
is  sawed  out  of  the  front  of  this  ring  to  allow  an  uninterrupted 
view  of  the  graduations,  and  it  is  wrapped  with  chamois  skin 
until  it  fits  as  snugly  as  desired.  A  spring  clamp  made  from 
sheet  brass  makes  a  more  elegant  upper  support.  By  this  simple 
arrangement  the  burette  may  be  raised,  lowered,  or  swung  to 

1  White  and  Campbell,  /.  Am.  Chem.  Soc,,  27,  734  (1905). 


GENERAL  METHODS  OF  TECHNICAL  GAS  ANALYSIS      17 

one  side  at  the  convenience  of  the  operator,  and  may  be  tipped 
in  any  position  while  carrying,  without  danger  of  breakage. 

By  reference  to  A  of  Fig.  6  it  will  be  seen  that  the  body  of 
the  burette  is  a  perfectly  straight  tube.  It  is  closed  at  the  bottom 
by  a  one-hole  rubber  stopper,  which  need  not  even  be  wired  in, 
unless  the  burette  is  to  be  filled  with  mercury.  To  clean  the 
burette,  all  that  is  necessary  is  to  take  out  the  rubber  stopper 
and  lift  the  burette  and  its  jacket  out  of  the  rings  when  it  may 
be  turned  upside  down,  swabbed  out  as  an  ordinary  burette, 
and  then  swabbed  with  a  clean  dry  muslin  which  is  more  efficient 
than  a  wet  cloth  in  removing  the  film  of  grease  which  causes 
the  drops  to  hang  to  the  glass.  Caustic  soda  may  be  used  or 
chromic  acid,  but  they  are  not  usually  necessary. 

4.  Care  of  Stopcock. — The  stopcock  of  a  gas  burette  is  very 
carefully  ground  and  polished  so  as  to  be  as  nearly  gas  tight  as 
possible.  Particles  of  grit  getting  into  the  capillary  opening 
are  apt  to  cut  a  groove  around  the  stopcock  so  the  opening  is 
bored  diagonally  in  order  that  the  grooves  worn  in  this  manner 
may  be  parallel  and  non-connecting.  This  device  is  of  assistance 
but  the  stopcock  must  still  be  handled  carefully. 

To  keep  in  good  condition  remove  the  stopcock  from  the 
burette,  wipe  it  off  with  a  dry  cloth  and  see  that  the  capillary 
openings  are  clean.  Do  the  same  with  the  seat  into  which  it 
fits  in  the  burette  and  the  capillaries  with  which  it  connects. 
Rub  a  thin  coat  of  some  lubricant  over  the  stopcock.  Vaseline 
is  inferior.  A  material  made  by  melting  one  part  of  best  black 
rubber  at  as  low  a  temperature  as  possible  and  stirring  into  it 
one  part  of  paraffine  and  one  part  of  vaseline  answers  well  when 
it  is  carefully  made.  The  author  has  found  anhydrous  lanolin 
the  best  material.  The  lubricated  stopcock  should  be  pressed 
gently  into  the  dried  seat  and  turned  a  couple  of  times,  when 
the  space  between  the  stopcock  and  the  seat  should  appear 
perfectly  translucent  without  air  bubbles  or  any  discontinuity. 
If  too  much  lubricant  is  used  it  will  work  itself  into  the  capillaries 
and  clog  them.  If  either  the  stopcock  or  the  seat  is  wet  the 
lubricant  will  not  adhere  well.  These  stopcocks  are  expensive 
and  it  is  advisable  to  fasten  them  to  the  burette  with  a  fine 
copper  wire  attached  to  the  stopcock  so  loosely  that  it  can 
turn  readily.  It  is  not  advisable  to  use  a  rubber  band  for  this 


18  GAS  AND  FUEL  ANALYSIS 

purpose  since  it  sticks  to  the  handle  of  the  stopcock  and  exerts 
a  torsion  sufficient  sometimes  to  turn  the  cock  at  an  inopportune 
time.  The  stopcock  should  always  be  loosened  in  its  seat  when 
the  burette  is  to  be  put  away  and  it  is  admirable  policy  to 
always  clean  it  and  make  it  ready  for  use  again  before  setting  it 
aside. 

5.  Saturating  the  Water  of  the  Burette.— The  liquid  filling 
the  burette  is  almost  always  water  which  allows  much  more 
rapid  and  convenient  and  in  some  ways  more  accurate  manipula- 
tion  than   mercury    does.     It   should   be   saturated   with   gas 
similar  to  that  which  is  to  be  analyzed.     If  the  gas  is  air  this 
precaution  may  often  be  omitted,  since  distilled  water  is  usually 
saturated  with  air.     The  precaution  should  not  be  omitted  with 
other  gases,  especially  those  like  flue  gases  rich  in  the  more 
soluble  carbon  dioxide.     The  errors  due  to  solubility  of  gases 
are  discussed  more  fully  in  Section  6  of  Chapter  I.     Place  200 
c.c.  of  water  in  a  flask  or  bottle  of  about  400  c.c.  capacity  and 
lead  in  a  stream  of  gas  through  a  glass  tube  passing  through  a 
loosely  fitting  cork,  shaking  occasionally.     If  the  supply  of  gas 
is  limited  a  smaller  flask  may  be  used  and  the  loose  cork  may 
be  pressed  down  tight  after  the  air  has  been  displaced.     Shaking 
the  flask  facilitates  absorption.     It  is  not  necessary  that  the 
water  be  absolutely  saturated  and  five  minutes  is  usually  ample 
time  for  the  operation. 

6.  Drawing  the  Sample  of  Gas  into  the  Burette. — The  gas 
to  be  analyzed  is  assumed  to  be  contained  in  a  gas  holder  of  a 
type  similar  to  that  shown  in  Fig.  4  of   Chapter   I,  but   the 
directions  for  use  of  this  type  of  gas  holder  may  readily  be 
adapted  to  other  types. 

The  tubing  to  connect  the  burette  and  gas  holder  should  be 
capillary  so  that  the  air  contained  in  it  may  be  completely 
swept  out  without  wasting  much  gas.  A  tube  of  1  mm.  internal 
diameter  answers  well.  It  should  not  be  rubber  because  rubber 
absorbs  heavy  hydrocarbons  from  gases  rich  in  these  bodies 
and  gives  them  back  again  to  gases  containing  them  in  but 
small  amount.  It  is  necessary  to  make  one  rubber  connection 
at  each  end  of  the  capillary  tube  but  the  surface  of  rubber 
exposed  to  the  action  of  the  gases  should  be  reduced  to  a  minimum 
by  bringing  the  ends  of  the  glass  capillary  tubes  into  direct 


GENERAL  METHODS  OF  TECHNICAL  GAS  ANALYSIS      19 

contact  with  each  other,  or,  if  it  is  necessary  to  leave  a  pinch- 
cock  on  the  rubber,  as  close  to  each  other  as  possible.  The 
glass  tubes  should  be  cut  off  square  and  the  sharp  edges  softened 
in  a  flame  sufficiently  to  prevent  the  cutting  of  the  rubber  but 
not  enough  to  constrict  the  capillary  opening  of  the  glass  tube. 
The  rubber  tube  should  fit  tightly  to  the  glass  and  be  of  the 
best  quality  black  gum  rubber,  free  from  any  internal  ridge 
where  the  seam  has  been  joined.  The  inside  of  the  rubber  tube 
may  be  moistened  with  water  or  preferably  with  glycerine  to 
make  it  slip  more  readily  over  the  glass.  The  rubber  connec- 
tions to  the  capillary  should  be  bound  with  wire  as  a  further 
safeguard  against  leakage.  Soft  copper  wire  of  about  22  B.  & 
S.  gage  is  suitable.  Finer  wire  is  too  apt  to  cut  the  rubber. 
Heavier  wire  is  apt  not  to  pull  up  snugly.  Copper  wire  of  24 
B.  &  S.  gage  insulated  with  cotton  and  paraffined  like  that 
used  for  annunciators,  is  the  best  material  as  it  is  strong  enough 
and  does  not  cut  the  rubber.  It  is  a  mistake  to  wrap  the  wire 
several  times  around  the  tube.  A  piece  of  wire  about  2  in. 
long  should  be  wrapped  once  around  the  tube.  The  crossed 
ends  are  then  to  be  grasped  close  to  the  rubber  with  a  pair  of 
pliers  and  tightened  with  a  single  half  turn  of  the  wrist. 

No  rubber  joint  can  be  relied  on  to  be  gas-tight  for  a  long 
period  of  time.  A  joint  prepared  as  directed  here  should,  how- 
ever, not  allow  any  perceptible  leakage  in  the  course  of  a  gas 
analysis  although  it  is  wiser  not  to  subject  it  to  any  higher  gas 
pressure  or  suction  than  necessary. 

The  method  of  connecting  the  gas  holder  and  the  burette 
is  shown  in  Fig.  7  where  A  is  the  gas  holder,  D,  a  bent  capillary 
tee  tube  and  F  the  gas  burette.  Before  making  the  connections 
the  gas  burette  is  to  be  filled  with  saturated  water  and  the  cock 
closed  by  a  turn  of  180°  which  completely  seals  both  the  capil- 
laries below  and  above  the  cock.  The  capillary  tee  tube  is  to 
be  inserted  into  the  open  rubber  tube  above  the  clamp  B,  con- 
nected at  E  as  shown  and  the  joints  are  to  be  wired.  The  gas 
in  the  holder  is  to  be  put  under  pressure  by  raising  the  levelling 
bottle  and  clamp  B  opened.  Cock  C  is  then  opened  slightly 
until  the  water  in  the  capillary  of  the  gas  holder  rises  to  displace 
all  the  air  in  the  funnel  arm.  Cock  C  is  then  closed  and  cock  F 
turned  90  degrees  to  the  position  shown  in  Fig.  7  and  at  B  in 


20 


GAS  AND  FUEL  ANALYSIS 


Fig.  6.  The  rest  of  the  water  in  the  capillary  A  moves  through 
D  and  out  F  driving  all  air  ahead  of  it.  Some  gas  may  also 
blow  out  if  the  manipulator  is  not  skilful,  but  this  does  no 
harm.  Cock  F  is  then  turned  90  degrees  opening  the  passage 
to  the  burette  as  shown  at  A  in  Fig.  6  and  the  gas  passes  into 
the  burette.  When  enough  gas  is  in  the  burette  another  90- 


FIG.  7. — Gas  burette  and  gas  holder. 

degree  turn  of  the  cock  in  the  same  direction  to  the  position  C 
of  Fig.  6  stops  the  gas  flow.  A  few  cubic  centimeters  of  water 
are  placed  in  the  funnel  above  C  (Fig.  7),  the  pressure  in  the 
gas  holder  is  changed  to  suction,  cock  C  is  opened  and  water 
flows  into  the  capillary  of  the  gas  holder  re-establishing  the 
seal.  The  clamp  B  may  then  be  closed  and  the  capillary 
disconnected.  This  procedure  allows  transfer  of  the  gas  without 


GENERAL  METHODS  OF  TECHNICAL  GAS  ANALYSIS      21 

possibility  of  change  in  composition  and  restores  the  seal  of 
the  gas  holder  at  the  close  of  the  operation.  Instead  of  the 
tee  with  cock  and  funnel  blown  as  one  piece  the  simpler  apparatus 
shown  in  Fig.  4  of  Chapter  I  may  be  used. 

7.  Measuring  a  Gas  Volume. — The  volume  of  gas  is  to  be 
measured  at  the  temperature  of  the  water  jacket  and  at  baro- 
metric pressure.  The  temperature  of  the  gas  as  drawn  into 
the  burette  does  not  ordinarily  differ  very  many  degrees  from 
that  of  the  jacket  water  but  it  should  be  allowed  to  stand  a 
few  moments  to  allow  it  to  attain  that  temperature.  During 
these  minutes  the  gas  if  not  already  saturated  with  moisture 
rapidly  absorbs  it  from  the  moist  burette  walls  and  becomes 
saturated  as  it  should  be  before  its  volume  is  measured. 

Delay  in  reading  the  volume  is  also  necessary  to  allow  the 
film  of  water  which  adheres  to  the  burette  walls  as  the  sample 
is  rapidly  drawn  in,  to  run  down.  If  the  walls  of  the  burette 
are  clean  the  water  will  have  run  down  in  three  minutes  so 
completely  that  the  volume  has  become  approximately  constant. 
If  this  precaution  is  neglected  the  volume  read  may  easily  be 
in  error  by  0.2  c.c.,  even  with  a  clean  burette.  Some  operators 
object  to  this  three-minutes  wait  as  too  great  hindrance  to  rapid 
work  and  it  is  true  that  if  the  readings  are  made  by  a  skillful 
operator  immediately  after  the  introduction  of  the  gas,  the 
errors  of  successive  readings  are  almost  constant  and  disappear 
in  the  subtractions.  If,  however,  the  practice  is  followed  of 
detaching  the  used  pipette  and  connecting  the  new  one  before 
reading  the  volume  of  gas,  sufficient  time  will  have  elapsed 
without  the  operator's  having  been  idle. 

To  obtain  a  sample  of  exactly  100  c.c.  a  sample  of  slightly 
more  than  100  c.c.  is  initially  taken  and  compressed  by  raising 
the  levelling  bottle  until  the  bottom  of  the  meniscus  is  exactly 
opposite  the  100  c.c.  mark.  The  stopcock  at  the  bottom  of 
the  burette  is  then  closed  so  that  the  meniscus  cannot  change  its 
position  and  the  stopcock  at  the  top  of  the  burette  opened  momen- 
tarily to  the  air,  to  allow  the  pressure  in  the  burette  to  equalize 
itself  with  the  outside  air.  The  volume  of  gas  should  now  be 
100  c.c.  at  atmospheric  pressure  but  the  correctness  of  the 
volume  should  be  checked  by  opening  the  stopcock  connecting 
the  levelling  bottle  with  the  burette  and  raising  the  levelling 


22  GAS  AND  FUEL  ANALYSIS 

bottle  until  its  water  surface  is  at  the  same  height  as  that  of  the 
water  in  the  burette.  The  connecting  stopcock  may  now  be 
closed  and  the  volume  read  as  indicated  by  the  bottom  of  the 
meniscus.  If  the  operation  has  been  properly  carried  out  the 
volume  should  be  exactly  100  c.c.  This  volume  is  subject  to 
correction  for  error  in  the  burette  and  if  an  exact  100  c.c.  sample 
is  desired  the  meniscus  may  have  to  be  set  on  some  other  figure 
than  the  100  mark. 

8.  Calibration  of  a  Gas  Burette. — A  gas  burette  may  be 
calibrated  like  any  other  form  of  burette  by  wiring  a  one-hole 
rubber  stopper  carrying  a  stopcock  into  the  bottom  of  the 
burette  and  weighing  the  water  delivered.  Burettes  of  good 
quality  are  usually  calibrated  accurately  enough  throughout 
their  cylindrical  portion  to  make  this  form  of  calibration  unneces- 
sary for  technical  work.  The  burette  should,  however,  be  cali- 
brated in  its  upper  portion,  especially  if  its  previous  history 
is  not  definitely  known,  since  its  original  stopcock  may  have 
been  broken  and  the  volume  of  the  neck  changed  when  a  new 
stopcock  was  fused  on,  and  since  it  may  have  been  calibrated 
by  the  maker  to  be  used  when  filled  with  mercury  instead  of 
with  water.  The  error  in  this  latter  case  arises  from  the  custom 
of  reading  the  mercury  meniscus  at  the  top  of  its  convex  surface 
and  the  water  meniscus  at  the  bottom  of  its  concave  surface. 
It  will  be  readily  seen  that  if  the  mercury  meniscus  stands  at 
10  c.c.  there  will  be  more  gas  in  the  burette  than  if  the  same 
burette  is  filled  with  water  with  the  bottom  of  its  meniscus  at 
10  c.c.  This  error  may  amount  to  0.2  c.c.  in  an  ordinary  burette. 
Both  of  these  errors  are  constant  ones  throughout  the  cylindrical 
portion  of  the  burette  and  independent  of  the  volume  of  gas  in  the 
burette.  It  will  therefore  be  sufficient  to  determine  them  once. 

The  most  convenient  method  is  to  compare  one  burette  with 
another.  Draw  into  each  burette  about  10  c.c.  of  air,  the 
exact  amount  being  entirely  immaterial.  It  is  only  necessary 
that  the  volume  be  large  enough  so  that  the  reading  is  in  the 
cylindrical  portion  of  the  burette.  It  is  not  desirable  that  the 
volume  be  large  since  the  error  caused  by  water  adhering  to 
the  walls  of  the  burette  increases  with  the  size  of  the  sample. 
Connect  the  burettes  by  a  bent  capillary  tube  making  the 
rubber  connections  while  the  stopcock  of  one  of  the  burettes  is 


GENERAL  METHODS  OF  TECHNICAL  GAS  ANALYSIS     23 

open  to  the  air  so  that  the  air  enclosed  in  the  capillary  will  be 
under  atmospheric  pressure.  Read  the  volume  of  the  air  in 
each  burette  at  atmospheric  pressure  as  usual.  We  will  assume 
that  Burette  A  which  has  an  unknown  constant  error  "x"  is 
the  one  being  tested  and  that  Burette  B  is  the  one  assumed  to 
be  correct  throughout  its  cylindrical  portion,  although  it  may 
itself  have  a  similar  unknown  constant  error  "  y. "  Transfer 
all  of  the  air  from  A  to  B  stopping  the  water  in  A  just  at  the 
stopcock  and  read  the  new  volume  in  B.  The  notes  will  then 
read  somewhat  as  follows: 

CALIBRATION  OF  BURETTE  A  AGAINT  BURETTE  B 

Burette  A  B 

Initial  vol.  air  10.6  c.c.+x          9.5  c.c.-f  y 
Second  reading       0  20.3  c.c.+y 


Subtracting      10.6  c.c.+x  =   10.8  c.c. 
x  =  +0.2.  c.c. 

This  result  translated  into  words  means  that  there  must  be 
added  to  each  reading  of  Burette  A  0.2  c.c.  Since  the  probable 
error  of  observation  is  0.1  c.c.  several  successive  determinations 
should  be  made  and  the  mean  taken. 

It  is  always  wiser  to  record  this  error  in  the  notebook  after 
each  reading,  92.5+0.2,  and  not  simply  make  the  correction 
mentally  and  record  92.7,  since  there  may  always  come  a  time 
when  the  analyst  will  be  in  doubt  as  to  whether  he  has  made 
the  mental  correction  or  forgotten  to  make  it  before  recording. 
This  error  automatically  disappears  whenever  one  volume  is 
subtracted  from  another  and  it  is  therefore  only  necessary  to 
apply  it  when  the  absolute  volume  needs  to  be  known  as  is  the 
case  with  the  initial  volume  taken  for  analysis.  This  makes 
the  error  vastly  less  important  than  it  would  be  otherwise,  for 
if  in  an  analysis  of  flue  gas  an  apparent  100  c.c.  sample  is  taken 
which  becomes  when  corrected  100.2  c.c.,  and  10  c.c.  is  found 
to  be  CO2,  the  percentage  of  CO2,  neglecting  the  burette  calibra- 
tion, is  found  to  be  10.00  per  cent,  and  allowing  for  the  calibra- 
tion 9.98  per  cent.,  which  when  rounded  off  becomes  10.0  per 
cent,  as  before.  The  ca,se  is  different,  however,  when  a  sample 
of  10.0  c.c.  is  taken  as  is  the  case  in  explosion  analysis.  If  the 


24 


GAS  AND  FUEL  ANALYSIS 


analysis  showed  8.0  c.c.  of  hydrogen,  the  percentage  neglecting 
the  calibration  would  be  figured  as  80.0  per  cent,  but  allowing 
for  the  calibration  would  be  78.4  per  cent.  It  is  preferable  to 
record  the  calibration  correction  even  though  it  may  be  later 
neglected  in  the  calculation. 

9.  Gas  Pipettes. — The  various  gases  are  determined  so  far 
as  possible  by  absorption  in  suitable  reagents  contained  in 
pipettes  of  the  form  shown  in  A,  B,  and  C  of  Fig.  8.  The  use  of  a 
separate  pipette  for  each  reagent  was  first  brought  into  general 
use  by  Hempel.  These  pipettes  differ  from  his  in  the  elimination 
of  the  deep  U  bend  in  the  capillary,  which  is  retained  only  in  the 
explosion  pipette.  This  deep  bend  is  a  distinct  disadvantage 


A. 


C. 


FIG.  8. — Details  of  gas  pipettes. 

since  drops  of  reagent  collect  in  it  and  are  later  carried  into  the 
burette.  It  is  no  longer  needed  when  used  with  the  burette 
just  described.  These  pipettes  are  mounted  on  wooden  stands, 
as  shown  in  Fig.  5,  which  should  be  paraffined  and  not  shel- 
lacked so  that  they  may  not  be  affected  by  reagents  accidentally 
spilled. 

10.  Connecting  the  Burette  and  Pipette. — The  greatest 
manipulative  error  with  most  forms  of  gas  analysis  apparatus 
comes  from  the  frequent  changes  of  pipettes  necessary.  Unless 
the  operator  is  skilful  there  is  danger  of  loss  of  gas  or  inclusion 
of  air.  The  form  of  burette  just  described  prevents  this  error. 
The  general  arrangement  of  the  burette  and  pipette  is  shown  in 
Fig.  5.  The  stopcock  A  is  turned  to  the  position  shown  at  B  in 


GENERAL  METHODS  OF  TECHNICAL  GAS  ANALYSIS     25 

Fig.  6,  the  bent  capillary  B  whose  dimensions  are  immaterial, 
is  connected  to  the  burette  and  pipette  and  the  rubber  joints 
are  wired.  The  operator  blows  through  the  rubber  tube  (D  of 
Fig.  5)  on  the  last  bulb  of  the  pipette,  forces  the  liquid  from  the 
pipette  up  the  capillary  and  over  to  the  stopcock,  driving  all 
the  air  ahead  of  it,  and  closes  the  stopcock  by  turning  it  90° 
to  the  position  D  of  Fig.  6.  The  capillary  tube  is  now  entirely 
full  of  liquid  and  the  operator  has  only  to  compress  the  gas  in 
the  burette  by  raising  the  levelling  bottle,  and  turn  the  stopcock  a 
half  turn  to  the  proper  position  (A  of  Fig.  6)  when  the  gas  will 
pass  into  the  pipette.  By  this  method  of  manipulation,  it  is 
easy  to  transfer  the  gas  from  burette  to  pipette  without  loss  or 
inclusion  of  air.  Furthermore,  since  the  volume  of  the  capillary 
is  entirely  immaterial,  it  may  be  chosen  of  larger  diameter  than 
usual,  permitting  more  rapid  work  and  lowering  the  pressure 
necessary  to  force  the  gas  through  it  rapidly.  It  has  been 
found  advantageous  to  have  the  stopcock  left-handed,  as  indi- 
cated, so  that  the  hand  manipulating  the  stopcock  may  not 
interfere  with  a  clear  view  of  the  meniscus  of  the  liquid  advancing 
along  the  capillary  tube. 

11.  Details  of  a  Simple  Gas  Analysis. — Accuracy  in  gas 
analysis  is  dependent  on  the  exercise  of  very  great  care  in  ma- 
nipulation. When  the  analysis  is  completed  there  is  no  way  of 
going  back  over  the  ground  again  as  may  so  frequently  be  done 
in  ordinary  chemical  analysis,  and  it  is  not  always  possible  to 
make  duplicate  analyses.  The  analyst  must  be  able  to  state 
with  confidence  that  every  precaution  was  taken  to  ensure  an 
accurate  result.  Detailed  directions  will  be  given  for  the 
analysis  of  a  gas  which  may  be  assumed  to  be  air.  This  is  a 
very  convenient  material  for  practice  since  it  may  be  obtained 
in  unlimited  quantities  and  of  practically  constant  composition. 

The  burette  is  to  be  cleaned  (§  3),  the  stopcock  lubricated 
(§4),  and  the  water  saturated  (§5).  Draw  the  sample  of  gas 
into  the  gas  burette  (§6),  measure  it  (§  7),  and  connect  it  to  a 
pipette  containing  NaOH  (§  10),  for  determination  of  CO2. 
The  connections  having  been  properly  made  and  the  air  driven 
out  of  the  capillary  tube  as  indicated,  raise  the  levelling  bottle 
and  pass  the  gas  into  the  absorbent,  letting  the  water  of  the 
burette  follow  until  it  reaches  the  bottom  of  the  capillary  of 


V 

26  GAS  AND  FUEL  ANALYSIS 

the  pipette.  The  gas  is  now  all  in  the  pipette.  Let  it  remain 
for  about  three  minutes  gently  shaking  the  pipette  occasionally 
to  agitate  the  gases  and  cause  more  rapid  absorption.  When 
it  is  believed  that  absorption  is  complete  pass  1  c.c.  of  the 
burette  water  into  the  pipette  to  rinse  from  the  capillary  any 
reagents  which  might  have  been  splashed  into  it,  and  then  draw 
back  the  gas  into  the  burette,  pulling  the  liquid  of  the  pipette 
as  far  as  the  stopcock  on  the  burette.  By  a  quarter  turn  of 
the  stopcock  to  position  B  of  Fig.  6  the  connection  between  the 
pipette  and  the  burette  is  closed  while  that  from  the  pipette  to 
the  air  is  open.  This  causes  the  reagent  to  siphon  back  into 
the  pipette.  After  waiting  for  three  minutes  to  allow  the 
liquid  to  drain  from  the  walls  of  the  burette  read  the  volume 
as  before  and  report  the  decrease  in  volume  as  the  volume  of  the 
C(>2  absorbed.  There  is  no  certainty  that  all  the  gas  has  been 
absorbed.  The  only  way  for  the  operator  to  be  sure  is  to  pass 
the  gas  back  again  into  the  pipette  and  repeat  the  operation 
until  the  volume  remains  constant.  Disconnect  the  pipette 
from  the  capillary  tube,  and  rinse  out  the  capillary  tube  with 
the  wash  bottle  shown  at  E  of  Fig.  5,  thus  completing  the  first 
step  of  the  analysis.  If  the  gas  being  analyzed  is  air,  the 
volume  after  treatment  with  NaOH  should  be  the  same  as  before 
since  the  volume  of  CO2  in  the  air,  0.04  per  cent.,  is  too  small  to 
be  measured  with  a  burette  of  this  type. 

In  the  practice  analysis  of  air  the  next  determination  would 
be  that  for  oxygen  which  would  be  absorbed  by  phosphorus, 
alkaline  pyrogallate  or  ammoniacal  copper  solution  as  directed 
in  §§  3,  4  and  5  of  Chapter  III.  Air  contains  20.9  per  cent,  of 
oxygen  by  volume.  The  residue  is  assumed  to  be  nitrogen. 

Successive  analyses  of  similar  gases  may  be  made  without 
changing  the  water  in  the  burette  provided  that  none  of  the 
reagents  have  been  carelessly  drawn  into  the  burette.  The 
greatest  danger  is  from  the  caustic  solution  which  will  absorb 
some  of  the  C02  from  a  newly  introduced  sample  before  its 
volume  has  been  measured.  Phenolphthalein  in  the  water  will 
act  as  an  indicator  to  show  when  it  has  become  alkaline  and 
should  be  changed.  There  is  no  objection  to  having  the  burette 
water  faintly  acid  and  there  is  the  advantage  that  small  amounts 
of  alkali  are  neutralized  and  rendered  harmless. 


GENERAL  METHODS  OF  TECHNICAL  GAS  ANALYSIS      27 

12.  Accuracy  of  the  Analysis. — Account  should  now  be 
taken  of  the  magnitude  of  various  possible  errors,  some  of 
which  have  not  been  mentioned.  The  smallest  division  on 
the  burette  is  usually  0.2  c.c.  and  the  volume  may  not  with 
certainty  be  estimated  by  interpolation  closer  than  0.1  c.c. 
This  probable  error  limits  the  accuracy  of  the  process  to  0.1  per 
cent,  with  a  sample  of  100  c.c.  and  an  accuracy  of  1.0  per  cent, 
with  a  sample  of  10  c.c.  Change  of  temperature  of  the  burette 
water  during  an  analysis  causes  a  change  of  0.36  per  cent,  in 
the  volume  of  the  gas  for  each  degree  centigrade.  Change  of 
barometric  pressure  causes  a  change  in  volume  of  0.13  per  cent, 
for  each  millimeter  of  mercury  change  in  pressure.  There  are 
other  minor  sources  of  error  which  will  be  mentioned  in  Chapter 
VI  under  "  Exact  Gas  Analysis."  It  will  be  evident  that  it  is 
perfectly  useless  to  expect  an  accuracy  of  greater  than  0.1  per 
cent,  with  apparatus  of  this  type,  and  that  an  error  of  0.2  per 
cent,  is  not  improbable.  An  analyst  who  reports  an  analysis 
carried  to  hundredths  of  a  per  cent,  only  shows  his  own  ignorance. 


CHAPTER  III 

ABSORPTION  METHODS  FOR  CARBON  DIOXIDE,  UN- 
SATURATED    HYDROCARBONS,    OXYGEN,    CARBON 
MONOXIDE  AND  HYDROGEN 

1.  Carbon  Dioxide. — This  gas  is  determined  by  absorption 
in  a  strong  solution  of  either  caustic  soda  or  potash.     Very 
concentrated  solutions  dry  the  gas  and  make  it  necessary  to 
let  it  stand  in  the  burette  before  reading  the  volume  until  it 
has  again  become  saturated  with  moisture.     Dilute  solutions 
work  too  slowly.     A  solution  of  50  grm.  NaOH  in  150  c.c.  of 
water  is  recommended  to  be  kept  in  the  form  of  pipette  shown 
in  A  of  Fig.  8.     The  absorption  is  rapid,  three  minutes  being 
always   ample.     The   reaction  may   be   accelerated   by  gently 
shaking  the  pipette  or  by  passing  the  gas  back  and  forth.     Glass 
rods  or  perferably  glass  tubes  are  sometimes  introduced  into 
the  pipettes  to  accelerate  the  absorption  by  offering  a  large 
wetted  surface  with  which  the  gas  may  come  in  contact.     If 
this  device  is  used  care  must  be  taken  that  no  gas  bubbles  are 
trapped  in  the  pieces  of  glass  tubing  as  may  frequently  be  the 
case  if  they  are  less  than  5  mm.  internal  diameter  or  if  they  do 
not  stand  vertically.     If  it  is  desired  to  place  glass  tubes  in  the 
pipette  use  the  form  shown  in  B  of  Fig.  8.     It  will  be  necessary 
to  wire  the  rubber  stopper  firmly  into  place  to  prevent  leakage 
of  the  caustic. 

This  reagent  absorbs  not  only  carbon  dioxide  but  also  sulphur 
dioxide,  hydrogen  sulphide  and  any  other  acid  vapors  which 
may  be  present.  It  may  be  used  until  almost  all  of  the  caustic 
has  been  changed  to  carbonate.  One  pipette  will  absorb  about 
four  liters  of  C02.  There  will  be  slow  carbonate  formation 
through  exposure  to  the  air  but  the  reagent  may  be  used  with- 
out fear  for  several  months  provided  it  is  used  infrequently. 

2.  Unsaturated  Hydrocarbons. — These  gases  are  determined 
by  absorption  in  a  liquid  which  by  addition  forms  saturated 
compounds  from  the  unsaturated  ones.     In  gases  from  coal  the 

28 


ABSORPTION  METHODS  29 

predominating  constituent  is  ethylene,  C2H4,  but  smaller  per- 
centages of  the  other  olefines  are  present  and  sometimes  small 
amounts  of  acetylene,  C2H2.  A  solution  of  bromine  water 
made  by  diluting  one  volume  of  saturated  bromine  water  with  two 
volumes  of  water  is  the  reagent  preferred  by  the  author.  It  is 
placed  in  the  first  bulb  of  the  double  pipette  shown  in  C  of 
Fig.  8,  and  the  third  bulb  is  filled  with  water  to  lessen  the  diffu- 
sion of  bromine  into  the  air  of  the  laboratory.  If  the  solution 
becomes  bleached  through  formation  of  hydrobromic  acid  in  the 
sunlight,  it  is  sufficient  to  add  a  few  drops  of  liquid  bromine  which 
again  brings  it  up  to  its  normal  strength.  It  is  unnecessary  to 
have  it  so  strong  that  the  gas  drawn  back  into  the  pipette  shows 
pronounced  yellow  bromine  fumes.  When  gases  with  more 
than  a  small  per  cent,  of  unsaturated  hydrocarbons  are  brought 
into  contact  with  bromine  it  is  possible  to  observe  the  formation 
of  the  bromide  as  an  oily  film  on  the  surface  of  the  liquid.  As 
this  film  retards  reaction  between  the  bromine  and  the  gas,  it  is 
advisable  to  shake  the  pipette  gently  during  absorption,  when 
little  drops  of  the  heavier  ethylene  bromide  may  be  seen  falling 
to  the  bottom  of  the  pipette.  The  gas  drawn  back  into  the 
burette  will  contain  so  much  bromine  vapor  that  its  volume 
may  even  have  increased  in  the  process.  It  must  be  passed  into 
a  caustic  solution  and  shaken  for  about  one  minute  to  remove 
the  bromine  fumes  and  then  brought  back  into  the  burette  and 
measured.  The  diminution  in  volume  is  to  be  reported  as 
unsaturated  hydrocarbons.  A  delicate  test  for  the  complete 
removal  of  these  constituents  is  afforded  when  phosphorus  is 
subsequently  used  as  a  reagent  for  oxygen.  A  fraction  of  a 
tenth  of  a  per  cent,  of  ethylene  will  completely  prevent  the 
reaction  between  phosphorus  and  oxygen.  Three  minutes 
shaking  with  the  bromine  is  sufficient  to  remove  the  unsaturated 
hydrocarbons  from  most  gases,  but  gases  of  high  candle  power, 
like  Pintsch  gas,  sometimes  require  ten  minutes.  Treatment 
with  bromine  water  should  be  repeated  until  phosphorus  smokes 
when  the  gas  is  brought  in  contact  with  it. 

Fuming  sulphuric  acid  acts  in  the  same  way  as  bromine  water, 
but  it  is  difficult  to  handle,  attacks  rubber  tubing  badly,  and 
must  be  protected  from  the  moisture  of  the  air  to  avoid  loss  of 
efficiency. 


30  GAS  AND  FUEL  ANALYSIS 

3.  Oxygen  by  Phosphorus. — Yellow  phosphorus  is  an  extremely 
reliable  reagent  for  the  absorption  of  oxygen  when  used  under 
proper  conditions.  It  combines  with  oxygen  producing  solid 
oxides  of  phosphorus  and  reacts  with  almost  no  other  gases 
which  might  be  present.  The  disadvantage  attending  its  use 
is  the  danger  of  the  reaction  not  taking  place  at  all  because 
of  the  presence  of  poisons,  because  of  too  low  temperature  or 
because  of  too  high  a  concentration  of  oxygen  in  the  gas.  There 
is,  however,  easy  ocular  evidence  of  the  reaction  so  that  there 
need  be  no  uncertainty  as  to  whether  the  reaction  has  taken 
place.  When  once  started  it  goes  to  completion. 

The  pipette  is  of  the  form  shown  in  B  of  Fig.  8.  To  prepare 
it  for  use  the  pipette  is  inverted  and  filled  with  water  and  into 
it  are  dropped  sticks  of  phosphorus  about  5  mm.  in  diameter 
which  have  been  cut  to  proper  length  under  water.  The  sticks 
are  to  stand  vertically  and  fill  the  pipette  practically  full.  The 
only  advantage  of  the  small  sticks  lies  in  their  greater  surface 
and  in  the  convenience  with  which  the  pipette  may  be  filled.  It 
is  possible  to  prepare  them  in  the  laboratory  by  melting  phos- 
phorus under  water  at  a  temperature  a  little  above  44°  C.  and 
sucking  it  into  a  slightly  conical  glass  tube.  With  expert 
manipulation  this  tube  may  be  lifted  from  the  warm  water  and 
plunged  into  cold  water  where  the  phosphorus  will  soldify  and 
contract  so  that  the  stick  may  be  pushed  from  the  tube.  It  is 
simpler  though  not  so  elegant  to  mould  the  sticks  in  a  tin  dish 
about  5  in.  long  made  with  a  corrugated  bottom  and  provided 
with  a  rim  about  an  inch  high  and  a  handle.  This  mould 
is  submerged  in  a  dish  of  warm  water  and  enough  phosphorus 
melted  in  it  to  fill  the  corrugations.  It  is  then  lifted  out  and 
placed  in  cold  water  till  the  sticks  become  solid.  Molten  phos- 
phorus catches  fire  instantly  in  the  air  and  produces  dangerous 
burns  on  the  skin.  Particles  of  solid  phosphorus  dropped  in 
cracks  of  a  wet  table  or  floor  have  been  known  to  smoulder 
twenty-four  hours  and  finally  burst  into  flame.  Great  care 
must  always  be  exercised  in  handling  phosphorus  and  it  is 
usually  preferable  to  buy  it  already  cast  in  small  sticks.  The 
pipette  should  be  kept  in  the  dark  when  not  in  use  to  avoid  the 
deterioration  of  the  phosphorus.  Pipettes  made  from  brown  glass 


ABSORPTION  METHODS  31 

retard  the  action  of  the  sunlight.  With  proper  care  a  phos- 
phorus pipette  should  last  for  years  without  refilling. 

When  a  gas  containing  oxygen  is  introduced  into  a  phosphorus 
pipette  there  normally  appears  at  once  a  dense  white  cloud  of 
oxides  of  phosphorus  which  are  evident  even  when  the  amount 
of  oxygen  is  less  than  0.1  per  cent,  of  the  total  volume.  All  tech- 
nical gases  will  contain  this  much  oxygen,  for  even  if  they  did 
not  contain  it  originally  they  will  have  absorbed  it  from  the  water 
of  the  sampling  apparatus  or  of  the  burette,  so  that  the  presence 
of  these  clouds  is  a  sure  indication  that  the  reaction  is  progressing 
properly.  Conversely  the  absence  of  any  smoke  means  not  that 
there  is  no  oxygen  present,  but  that  there  is  something  preventing 
the  reaction.  The  reaction  between  oxygen  and  phosphorus 
is  also  attended  by  a  glow,  visible  only  in  the  dark,  which  disap- 
pears with  the  completion  of  the  reaction.  The  white  cloud  con- 
sists of  solid  particles  of  phosphoric  oxides  which  slowly  settle  and 
dissolve  in  the  water.  It  is  not  necessary  to  wait  for  this,  how- 
ever, before  drawing  the  gas  back  into  the  burette  and  measuring 
the  oxygen  absorbed  for  the  particles  possess  very  slight  vapor 
tension  and  do  not  occupy  an  appreciable  volume.  The  reaction 
should  with  certainty  be  completed  in  three  minutes  if  the  white 
smoke  appears  promptly  and  if  the  surface  of  phosphorus  exposed 
is  large.  It  will  not  accelerate  the  reaction  to  shake  the  pipette 
since  the  reagent  is  a  solid  and  the  pipette  is  so  closely  filled 
with  sticks  that  diffusion  will  soon  bring  the  oxygen  to  the  sur- 
face of  the  phosphorus. 

The  sticks  of  phosphorus  at  first  yellow  and  waxy  become 
covered  with  a  reddish  crust  on  long  exposure  to  light  and  are  in- 
active. Such  sticks  may  be  melted  under  water,  skimmed,  and 
cast  into  new  sticks.  The  inactive  crust  may  also  be  removed 
by  placing  in  the  pipette  a  10  per  cent,  solution  of  K2Cr2O7 
made  faintly  acid  with  H2SO4.  The  chromate  becomes  reduced 
to  the  green  chromic  salt  with  oxidation  of  the  surface  of  the 
phosphorus.  It  is  preferable,  however,  to  avoid  deterioration 
by  keeping  the  pipette  in  the  dark  when  it  is  not  in  use. 

If  the  white  vapors  do  not  appear  promptly  when  the  gas  is 
passed  into  the  pipette,  the  explanation  may  be  sought  in  four 
directions. 

a.  The  temperature  may  be,  too  low.     It  should  be  above  15°  C. 


32  GAS  AND  FUEL  ANALYSIS 

b.  The  concentration  of  the  oxygen  may  be  too  high.     Moist 
phosphorus  does  not  react  at  all  with  perfectly  pure  oxygen  at 
ordinary  room  temperature.     If  the  partial  pressure  of  the  oxygen 
is  diminished  either  mechanically  by  an  air  pump  or  by  dilution 
with  an  inert  gas  the  reaction  commences.     With  50  per  cent, 
oxygen  it  is  violent,  flame  being  produced  and  the  phosphorus 
melting.     There  is  danger  of  breaking  the  pipette.     When  the 
concentration  is  less  than  30  per  cent,  the  reaction  proceeds 
quietly  and  the  phosphorus  does  not  melt. 

c.  A  poison  may  be  present.     The  most  commonly  occurring 
poison  is  ethylene,  a  few  hundredths  of  a  per  cent,  of  which  com- 
pletely prevents  the  reaction  between  phosphorus  and  oxygen. 
Acetylene,  benzine,  ether,  hydrogen  sulphide  and  many  other 
substances  possess  similar  though  usually  weaker  powers.     For- 
tunately they  are  practically  all  Removed  either  mechanically  or 
chemically  by  bromine  water  followed  by  caustic  potash  and  the 
gas  should  always  be  thus  treated  if  the  white  fumes  fail  to  appear 
promptly. 

d.  The  phosphorus  may  have  been  rendered  inactive  by  a 
heavy  dose  of  poison.     It  may  be  restored  by  replacing  the  water 
in  the  pipette  with  fresh  water  and  passing  several  successive 
samples  of  air  into  the  pipette  until  the  phosphorus  again  smokes 
freely. 

Commercial  compressed  oxygen  should  be  diluted  with  nitro- 
gen before  analysis.  The  nitrogen  may  be  conveniently  pre- 
pared from  air  by  passing  a  buretteful  of  air  into  the  phosphorus 
pipette,  disconnecting  the  pipette  and  closing  it  with  a  pinchcock. 
Twenty-five  to  thirty  cubic  centimeters  of  the  oxygen  are  then 
to  be  drawn  into  the  burette  (note  that  a  calibration  error  of 
0.3  c.c.  means  1  per  cent,  here)  and  the  phosphorus  pipette  recon- 
nected. There  will  be  sufficient  nitrogen  in  it  to  flush  out  the 
capillary  connecting  tube  and  fill  the  burette  as  well.  The 
oxygen  may  now  be  absorbed  by  phosphorus.  It  is  desirable 
to  introduce  the  oxygen  into  the  burette  before  the  nitrogen 
which  thus  fills  the  upper  part  of  the  burette  and  comes  in  contact 
first  with  the  phosphorus.  If  the  reverse  procedure  were  fol- 
lowed and  the  oxygen  introduced  in  the  burette  last,  it  might 
be  brought  in  concentrated  form  in  contact  with  the  phosphorus 


ABSORPTION  METHODS  33 

and  cause  violent  combustion,  a  trouble  which  the  above  scheme 
of  procedure  avoids. 

It  has  been  frequently  noted  that  beginners  in  gas  analysis 
obtain  rather  consistently  low  results  when  determining  the  oxy- 
gen in  air.  This  is  usually  due  to  the  presence  of  sodium  carbon- 
ate in  the  water  of  the  burette  as  the  result  of  faulty  manipula- 
tion of  the  caustic  pipette.  The  water  in  the  phosphorus  pipette 
contains  phosphoric  acid  and  if,  in  the  manipulation,  some  of  this 
acid  is  drawn  back  into  the  burette  containing  a  little  alkali, 
carbon  dioxide  is  evolved  in  sufficient  amount  to  cause  the  ap- 
parent percentage  of  oxygen  in  the  air  to  be  a  few  tenths  of  a 
per  cent.  low. 

4.  Oxygen  by  Alkaline  Pyrogallate  or  Hydrosulphite.— Alka- 
line pyrogallate  is  very  frequently  used,  especially  in  apparatus 
of  the  Bunte  or  Orsat  type.  When  used  with  proper  precautions 
it  gives  accurate  results.  Pyrogallol  is  a  trihydric  phenol 
C6H3(OH)3  which  in  alkaline  solution  is  a  strong  reducing  agent, 
becoming  itself  oxidized  to  other  products.  Unfortunately,  un- 
less the  solution  is  freshly  prepared  and  strongly  alkaline  there 
is  danger  of  carbon  monoxide  being  evolved  as  oxygen  is  ab- 
sorbed. This  not  only  causes  the  oxygen  to  be  reported  low, 
but  also  makes  the  carbon  monoxide  high.  Berthelot  has  shown 
that  a  reagent  made  by  taking  a  solution  of  1  part  of  pyrogallol 
in  three  of  water  and  mixing  it  with  its  own  volume  of  a  solution 
of  1  part  of  KOH  in  two  of  water  will,  when  freshly  prepared, 
absorb  ten  times  its  volume  of  oxygen  without  giving  back  more 
than  a  trace  of  CO,  but  that  solutions  which  have  been  used  too 
long  or  do  not  contain  enough  alkali  may  give  up  as  much  as  5 
per  cent,  of  the  volume  of  oxygen  absorbed  as  carbon  monoxide. 

The  reagent  should  be  kept  in  a  double  pipette  (C  of  Fig.  8), 
the  third  bulb  being  filled  with  water  to  prevent  action  of  the 
air  on  the  reagent.  It  may  also  be  kept  in  a  single  pipette 
(A  of  Fig.  8)  provided  a  rubber  balloon  is  fastened  to  the  second 
bulb  for  the  same  purpose.  The  reagent  works  very  slowly  at 
temperatures  below  15°  C.  Carbon  dioxide  and  other  gases 
which  would  be  absorbed  by  alkali  must  be  removed  before 
testing  for  oxygen  with  pyrogallate. 

Mr.  H.  A.  Small  in  the  author's  laboratory  tested  the  behavior 
of  a  solution  of  pyrogallate  made  up  according  to  Berthelot's 
directions  and  kept  in  an  ordinary  four  bulb  pipette  without 


34  GAS  AND  FUEL  ANALYSIS 

any  special  precautions  to  prevent  diffusion  of  oxygen  into  the 
pipette.  Duplicate  samples  of  air  were  analyzed  almost  daily 
for  more  than  a  month.  During  the  first  four  weeks  the  reagent 
absorbed  the  proper  percentage  of  oxygen  although  it  was  fre- 
quently necessary  to  shake  more  than  three  minutes  to  accom- 
plish this.  The  150  c.c.  of  reagent  in  the  pipette  had  up  to  this 
time  absorbed  1140  c.c.  of  oxygen.  After  this  the  absorption 
of  oxygen  became  incomplete,  the  line  of  demarcation  being 
quite  sharp  and  the  apparent  oxygen  of  the  air  dropping  from 
20.7  per  cent,  to  20.4  per  cent.  Tests  showed  that  the  oxygen 
was  still  being  quantitatively  absorbed  but  that  about  0.3  per 
cent,  of  carbon  monoxide  was  being  evolved.  These  results  con- 
firm Berthelot's  statements.  According  to  our  results  1  c.c.  of 
the  reagent  absorbs  8.0  c.c.  of  oxygen.  In  case  of  doubt  concern- 
ing the  reagent  it  should  be  tested  on  air  and  should  be  rejected 
unless  it  absorbs  20.6  to  20.8  per  cent,  of  oxygen. 

Anderson1  recommends  a  much  more  strongly  alkaline  solution 
prepared  by  dissolving  15  g.  pyrogallol  in  100  c.c.  of  a  solution  of 
KOH  of  sp.  gr.  1.55.  An  alkaline  solution  of  this  concentration 
is  obtained  by  1.5  to  2.0  parts  of  KOH  in  1.0  parts  of  water. 
NaOH  cannot  be  substituted  for  KOH  in  this  concentrated  solu- 
tion. A  disagreeable  feature  of  this  concentrated  reagent  is  the 
formation  of  a  precipitate  which  chokes  the  glass  tubes  and  ren- 
ders it  difficult  to  determine  the  exact  level  of  the  liquid  when 
drawing  the  gas  back  into  the  pipette.  Anderson  has  described 
a  special  pipette  to  minimize  this  difficulty.  Each  cubic  centi- 
meter of  reagent  will  absorb  satisfactorily  22  c.c.  of  oxygen  from 
air  when  used  in  an  ordinary  Orsat  pipette.  The  absorption  is 
much  more  rapid  than  with  the  ordinary  reagent.  Anderson 
recommends  the  simple  Orsat  pipette  over  the  more  complicated 
forms,  for  use  with  this  reagent.  Sodium  hydrosulfite  has  been 
recommended  by  Franzen2  as  a  cheaper  and  better  reagent  than 
pyrogallol.  The  solution  is  prepared  by  dissolving  50  grm. 
Na2S2O4  in  250  c.c.  H20  and  mixing  this  with  40  c.c.  of  a  caustic 
solution  made  by  dissolving  500  grm.  NaOH  in  700  c.c.  H2O. 
Each  cubic  centimeter  of  this  reagent  absorbs  10.7  c.c.  oxygen. 
The  equation  for  the  reaction  is  as  follows  : 
Na2S204+H20  +  0  = 


lJour.  Ind.  and  Eng.  Chem.,  8,  131,  133  (1916). 
2  Chem.-Berichte,  39,  2069  (1906). 


ABSORPTION  METHODS  35 

The  solution  is  placed  in  a  pipette  containing  rolls  of  iron  gauze 
to  increase  the  absorbing  surface.  Franzen  states  that  the  ab- 
sorption is  complete  in  five  minutes  without  shaking,  that  it  pro- 
ceeds almost  as  rapidly  at  4°  C.  as  at  room  temperature,  and 
that  there  is  no  danger  of  the  formation  of  CO  in  the  process. 

5.  Oxygen  by  Ammoniacal  Copper  Solution. — Orsat1  advo- 
cated a  cold  saturated  solution  of  ammonia  and  ammonium  chlo- 
ride in  contact  with  metallic  copper  as  a  reagent  for  the  absorption 
of  oxygen  and  called  attention  to  the  limitation  in  the  use  of  this 
reagent  caused  by  its  absorption  of  carbon  monoxide.  Badger2 
has  recently  made  a  careful  study  of  various  modifications  of 
this  solution  and  recommends  that  the  reagent  be  prepared  by 
saturating  with  ammonium  chloride  a  mixture  of  one  part  con- 
centrated ammonia  and  one  part  water.  This  solution  will  ab- 
sorb from  fifty  to  sixty  times  its  volume  of  oxygen  and  then  fails, 
not  by  refusing  to  absorb  quantitatively  but  by  the  formation 
of  so  heavy  a  precipitate  that  it  becomes  unmanageable.  The 
presence  of  metallic  copper  in  the  gas  space  is  necessary  for  the 
proper  operation  of  this  reagent.  The  first  bulb  of  a  pipette  of 
the  type  of  B  in  Fig.  8  is  filled  with  copper  wires  placed  vertically 
and  long  enough  so  that  the  upper  ends  of  those  centrally  placed 
reach  even  into  the  outlet  of  the  capillary  tube.  This  precaution 
is  necessary  when  analyzing  nearly  pure  commercial  oxygen  as 
otherwise  the  liquor  rising  as  the  oxygen  is  absorbed  may  sub- 
merge all  of  the  wires  before  the  oxygen  is  all  absorbed.  A 
rubber  balloon  may  be  fastened  on  the  second  bulb  of  the  pipette 
to  prevent  rapid  absorption  of  oxygen  from  the  air.  This  reagent 
is  cleaner  to  use  and  has  a  longer  life  than  pyrogallate  and  its 
action  is  not  interfered  with  by  the  poisons  which  inhibit  the 
action  of  phosphorus.  It  is  active  at  almost  any  temperature. 
Ammonia  is  given  off  from  the  fresh  reagent  in  amount  sufficient 
to  make  it  necessary  to  pass  the  gas  into  a  pipette  containing 
dilute  sulphuric  acid  before  reading  the  volume  to  be  recorded 
as  that  of  the  gas  from  which  the  oxygen  has  been  removed.  An 
old  reagent  gives  off  very  little  ammonia.  This  solution  absorbs 
carbon  monoxide  and  also  acetylene  and  cannot  be  used  to  de- 
termine oxygen  when  these  gases  are  present.  It  is  recommended 
for  the  analysis  of  commercial  oxygen. 

1  Annales  des  Mines,  Series  7,  t.  8,  485  (1875). 

2  Jour.  Ind.  and  Eng.  Chem.,  12,  161  (1920). 


36  GAS  AND  FUEL  ANALYSIS 

6.  Carbon  Monoxide. — The  methods  for  absorption  of  CO 
are  less  satisfactory  than  for  any  of  the  other  commonly  occurring 
gases.  The  usual  reagent  is  cuprous  chloride  Cu2Cl2  which  on 
account  of  its  slight  solubility  in  water  must  be  used  either  in 
acid  or  ammoniacal  solution.  The  acid  solution  consists  of  a 
practically  saturated  solution  of  cuprous  chloride  in  hydrochloric 
acid  of  specific  gravity  of  approximately  1.12.  Since  the  acid 
is  only  a  solvent,  its  exact  concentration  is  immaterial.  Com- 
mercial acid  may  be  used.  About  150  grm.  of  the  cuprous 
chloride  will  dissolve  in  a  liter  of  acid  of  this  concentration. 
This  solution  of  cuprous  chloride  when  pure  is  perfectly  colorless 
but  it  darkens  through  slight  oxidation  as  on  exposure  to  the 
air,  so  that  the  usual  solutions  are  black.  It  is  possible  to  keep 
it  colorless  by  placing  in  the  reagent  bottle  or  in  the  pipette 
copper  turnings  or  copper  wire,  but  it  does  not  increase  the 
efficiency  of  the  reagent.  If  the  oxidation  proceeds  so  far  that 
the  solution  becomes  green,  due  to  complete  oxidation  to  the 
cupric  state,  the  solution  is  worthless  until  it  is  again  reduced 
to  the  cuprous  state. 

The  reagent  is  kept  in  a  double  pipette  whose  third  bulb  is 
filled  with  HC1  of  sp.  gr.  1.12  instead  of  water  so  that  in  case 
the  cuprous  chloride  spills  into  it,  it  will  not  be  precipitated. 
The  gas  which  must  have  been  previously  freed  from  unsaturated 
hydrocarbons  and  oxygen  is  passed  into  the  pipette  and  shaken 
for  three  minutes,  then  drawn  back  to  the  burette  and  passed 
into  a  second  pipette  containing  fresh  cuprous  chloride  where 
it  is  again  shaken  for  three  minutes,  drawn  back  and  measured. 
The  HC1  vapors  in  the  gas  may  be  neglected.  There  is  no 
method  of  knowing  whether  the  absorption  of  the  CO  has  been 
complete.  The  only  safe  way  is  to  repeat  the  absorption  using 
a  fresh  solution  until  the  volume  becomes  constant.  Usually 
two  absorptions  of  three  minutes  each  are  sufficient. 

The  reaction  between  carbon  monoxide  and  cuprous  chloride 
has  not  been  definitely  worked  out.  Jones1  has  shown  that 
under  certain  circumstances  a  crystalline  compound  of  definite 
composition  results — Cu2Cl2,  2CO.  4H2O.  In  the  dilute  solu- 
tions present  in  gas  analysis,  however,  the  reagent  behaves 

lAm.  Chem.  Jour.,  22,  287. 


ABSORPTION  METHODS  37 

exactly  as  if  it  dissolved  the  carbon  monoxide.  When  a  perfectly 
new  solution  is  used  the  CO  will  be  practically  completely 
removed.  As  the  CO  in  solution  increases  there  comes  appar- 
ently an  equilibrium  between  that  in  the  gas  and  that  in  the 
solution,  with  the  result  that  the  absorption  is  incomplete.  If 
a  gas  with  only  a  small  amount  of  CO  is  brought  in  contact 
with  a  solution  which  has  absorbed  much,  the  gas  will  increase 
in  volume  due  to  CO  given  up  by  the  solution.  Each  cuprous 
chloride  pipette  should  bear  a  label  on  which  should  be  recorded 
the  number  of  cubic  centimeters  of  carbon  monoxide  which  has 
been  absorbed.  When  it  has  absorbed  more  than  10  c.c.  it  is 
not  safe  to  rely  on  the  results.  In  practice  the  analyst  should 
have  two  pipettes  for  cuprous  chloride,  one,  which  has  absorbed 
considerable  carbon  monoxide,  to  be  used  first,  and  another, 
which  should  be  kept  almost  entirely  fresh  to  follow  the  other. 
When  this  second  pipette  has  absorbed  10  c.c.  of  CO  it  should 
be  used  as  the  first  pipette  and  the  former  first  pipette  should 
be  emptied  and  refilled  with  fresh  reagent.  The  solution  may 
be  regenerated  if  desired  by  boiling  it  for  half  an  hour  in  a  flask 
containing  some  metallic  copper  and  provided  with  a  reflux 
condenser  to  prevent  much  loss  of  acid.  The  feebly  held  CO  is 
driven  off  by  the  boiling  and  any  oxidized  solution  is  reduced  to 
the  cuprous  state  again. 

Krauskopf  and  Purdy1  suggest  the  use  of  stannous  chloride  as 
a  reducing  agent  to  be  added  to  a  solution  of  cupric  chloride  and 
form  cuprous  chloride  in  solution.  Their  solution  contained 
127.2  grams  metallic  copper  and  616  c.c.  of  concentrated  hydro- 
chloric acid  per  liter.  The  cupric  chloride  dissolved  in  the  hydro- 
chloric acid  was  reduced  by  the  stannous  chloride.  The  presence 
of  stannic  and  stannous  chlorides  even  in  relatively  large  amounts 
does  not  impair  the  efficiency  of  the  solution  for  the  absorption 
of  carbon  monoxide.  The  authors  report  that  200  c.c.  of  this 
solution  will  absorb  over  300  c.c.  of  carbon  monoxide  quantita- 
tively as  shown  by  the  following  extract  from  their  Table  I 
where  Pipette  I  contains  an  old  solution  and  Pipette  II  a  fresh 
solution,  used  after  Pipette  I  gave  no  further  absorption. 

1  /,  Ind,  Eng,  bhem.,  12,  158  (1920), 


38  GAS  AND  FUEL  ANALYSIS 

Amount  of  CO  already  absorbed  3(55. 5  e.c. 

Volume  of  gas  taken  50.2c.c. 

Pipette  I  Pipette  II 

Time,  Amount  CO  lime,  Amount  CO 

min.  absorbed  min.  absorbed 

1  39.0  1  0.4 

2  0.6  2  0.2 

3  0.2  3  0.0 

The  authors  also  confirm  the  reliability  of  the  process  of  regen- 
erating the  solution  by  heating  to  60-70°  C.  for  several  hours 
under  a  reflex  condenser. 

The  ammoniacal  solution  is  made  by  suspending  about  150 
grm.  of  cuprous  chloride  in  a  liter  of  distilled  water  into  which 
ammonia  gas  is  passed  until  the  liquid  becomes  a  pale  blue  color. 
The  ammoniacal  solution  slowly  regenerates  itself  on  standing, 
the  CO  becoming  oxidized  to  (NH4)2CO3  and  a  mirror  of  metallic 
copper  depositing.  The  NH3  gas  must  be  removed  by  an  acid 
pipette  before  the  correct  amount  of  CO  absorbed  may  be  read. 

Carbon  monoxide  may  be  estimated  by  explosion  or  combus- 
tion as  described  in  the  next  chapter.  Minute  amounts  of  it 
may  be  estimated  by  the  IzOs  method  given  in  Chapter  VI  on 
"Exact  Gas  Analysis." 

7.  Absorption  of  Hydrogen. — Hydrogen  may  be  absorbed  by 
palladium  sponge  superficially  oxidized  to  palladous  oxide, 
according  to  the  method  oi  Hempel.  It  is  necessary  to  re- 
generate the  palladium  after  each  experiment  and  the  reaction 
is  prevented  by  small  amounts  of  carbon  monoxide,  hydrochloric 
acid  and  other  constituents  so  that  it  is  not  a  method  which  has 
found  much  favor. 

A  solution  of  palladous  chloride  as  prepared  by  Campbell  and 
Hart1  is  a  better  reagent.  It  is  used  as  an  almost  neutral  1  per 
cent,  solution  prepared  by  dissolving  5  grm.  palladium  wire  in 
30  c.c  of  HC1  to  which  is  added  1  or  2  c.c.  HN03.  The  solution 
thus  prepared  is  evaporated  just  to  dry  ness  on  the  water  bath, 
redissolved  in  5  c.c.  of  HC1  (sp.  gr.  1.20)  and  25  or  30  c.c.  of 
water,  warmed  till  solution  is  complete  and  diluted  to  750  c.c. 
It  is  placed  in  a  simple  Hempel  pipette  made  to  be  readily 

1  Am.  Chem.  Jour.,  18,  294  (1896). 


ABSORPTION  METHODS  39 

detachable  from  its  frame  so  that  the  bulbs  may  be  placed  in  a 
water  bath.  The  first  bulb  of  the  pipette  should  have  a  capacity 
of  at  least  150  c.c.  to  allow  for  expansion  of  the  gas  and  water 
vapor  when  the  solution  is  warmed.  The  gas  freed  by  the  usual 
methods  from  CO2,  CnH2n,  02  and  CO,  and  containing  H2, 
CH4  and  N2  is  passed  into  the  pipette  and  the  water  from  the 
burette  passed  over  to  seal  the  capillary  of  the  pipette.  A  screw 
clamp  is  placed  on  the  rubber  connecting  tube  and  the  pipette 
disconnected  from  the  burette  and  placed  in  a  water  bath  at 
50°  C.  for  an  hour  and  a  half.  A  higher  temperature  does  no 
harm  provided  it  does  not  expand  the  gas  so  much  as  to  cause 
it  to  bubble  out  of  the  first  bulb  or  to  leave  only  a  small  amount 
of  reagent  in  contact  with  the  gas  in  the  first  bulb.  The  hydrogen 
reacts  with  the  palladium  chloride  forming  metallic  palladium 
and  HC1.  The  total  decrease  in  volume  is  reported  as  hydrogen. 
The  reagent  may  be  counted  on  to  absorb  one-third  of  its  volume 
of  hydrogen  completely  in  an  hour  and  a  half.  Larger  quanti- 
ties will  be  absorbed  more  slowly.  It  is  readily  regenerated  by 
rinsing  from  the  pipette,  evaporating  just  to  dry  ness  on  the 
water  bath,  dissolving  in  5  or  6  c.c.  HC1  and  4  or  5  drops  of 
HNOs  and  again  evaporating.  The  dry  palladous  chloride  is 
dissolved  by  adding  2  c.c.  cone.  HC1  and  a  small  amount  of 
water  and  is  then  diluted  to  its  original  volume.  The  method 
is  accurate  and  satisfactory.  Carbon  monoxide  and  other 
reducing  gases  behave  like  hydrogen  and  must  be  removed  pre- 
vious to  the  test  but  hydrocarbons  of  the  methane  series  are 
not  affected.  The  chief  objection  to  the  method  lies  in  the  time 
consumed  which  makes  it  frequently  necessary  to  correct  the 
gas  volumes  for  change  in  room  temperature  and  barometric 
pressure.  A  memorandum  should  be  made  of  the  temperature 
of  the  burette  jacket  and  of  the  barometric  pressure  before  and 
after  the  test  and  corrections  made  if  necessary. 

Paal  and  Hartmann1  recommend  a  solution  of  colloidal 
palladium  made  by  dissolving  2.44  grm.  collodial  palladium 
manufactured  according  to  Paal's  process  by  Kalle  (  =  1.5  grm. 
palladium)  and  2.74  grm.  of  sodium  picrate  in  enough  water  to 
bring  the  volume  to  130  c.c.  Gaseous  hydrogen  dissolves  in  the 
aqueous  palladium  solution  and  reduces  the  picric  acid.  Hempel 2 

1  Chem.  Berichte,  43,  243  (1910). 

2  Zeit.  Angewanat.  Chem.,  25,  1843  (1912). 


40  GAS  AND  FUEL  ANALYSIS 

has  made  a  critical  study  of  this  method  and  reports  that 
a  solution  prepared  in  this  manner  will  absorb  in  15  minutes 

when  freshly  prepared  21.2  c.c.  H2  per  1  c.c.  reagent, 
after  79  days  16.2  c.c.  H2  per  1  c.c.  reagent, 

after  1  year  1.6  c.c.  H2  per  1  c.c.  reagent. 

He  states  that  a  fresh  solution  may  be  safely  trusted  to  absorb 
completely  7.2  c.c.  H2  per  centimeter  reagent  in  three  minutes 
if  heated  to  the  temperature  of  the  blood.  He  advocates  the 
preparation  of  the  solution  in  small  quantities  and  its  use  in  a 
pipette  filled  mainly  with  mercury.  A  disadvantage  attending 
the  use  of  the  reagent  is  the  persistent  foam  which  results  after 
shaking  and  which  must  be  allowed  to  subside  before  the  volume 
of  the  gas  is  read.  A  few  drops  of  alcohol  at  once  dissipate 
the  foam  but  spoil  the  reagent  for  further  use.  When  alcohol  is 
used  the  pipette  must  be  carefully  cleaned  before  another 
experiment. 

In  using  this  method  the  gas  must  first  be  freed  from  oxygen 
which  is  caused  to  unite  with  the  hydrogen  by  the  palladium, 
from  unsaturated  hydrocarbons  which  form  addition  products 
with  the  hydrogen,  and  from  carbon  monoxide  which  retards 
the  absorption  of  the  hydrogen.  Bromine  is  recommended  as 
the  absorbent  for  the  unsaturated  hydrocarbons  as  it  removes 
compounds  of  arsenic  and  phosphorus  which  might  retard  the 
catalytic  action.  Alkaline  pyrogallate  is  advised  for  absorption 
of  oxygen  as  phosphorus  fumes  affect  the  palladium.  An 
ammoniacal  solution  of  copper  chloride  is  preferred  to  the  acid 
solution. 

8.  General  Scheme  of  Analysis. — Fig.  9  shows  the  apparatus 
ready  for  the  analysis.  The  details  concerning  the  individual 
steps  of  the  process  were  given  in  Chapter  II  but  it  is  well  to 
recapitulate  the  important  points  in  connection  with  the  general 
scheme  of  analysis.  The  water  of  the  burette  is  saturated  with 
gas  similar  to  that  which  is  to  be  analyzed  and  a  sample  of  ap- 
proximately 100  c.c.  is  then  drawn  in  and  the  volume  read  at 
atmospheric  pressure  after  three  minutes  have  been  allowed  to 
elapse  so  that  the  surplus  water  will  have  drained  from  the  bur- 


ABSORPTION  METHODS 


41 


ette  walls.  Any  needed  correction  for  burette  error  is  to  be 
applied  to  this  reading.  The  caustic  soda  pipette  is  to  be  con- 
nected to  the  burette,  and  the  gas  passed  into  it  and  allowed  to 
remain  with  gentle  shaking  for  three  minutes.  C(>2  is  absorbed, 
as  well  as  H2S,  SO2  etc.,  the  whole  being  usually  reported  as  CO2. 
The  gas  is  drawn  back  into  the  burette  and  while  waiting  for  the 
excess  water  on  the  burette  walls  to  run  down,  the  capillary 
connecting  tube  is  flushed  out  and  the  bromine  water  pipette 


. 
FIG.  9. — Assembled  apparatus  for  gas  analysis. 

is  connected.  The  volume  in  the  gas  burette  is  then  read,  and 
the  gas  passed  into  the  bromine  water  where  it  is  shaken  for  three 
minutes.  It  is  drawn  back  to  the  burette,  and  at  once  passed 
into  the  caustic  pipette  where  it  is  shaken  one  minute  to  re- 
move bromine  fumes.  It  is  then  drawn  back  into  the  burette 
and  the  decrease  in  volume  reported  as  unsaturated  hydrocar- 


42  GAS  AND  FUEL  ANALYSIS 

bons.  The  gas  is  next  passed  into  the  phosphorus  pipette. 
White  smoke  at  once  appears.  If  it  does  not,  it  is  a  sign  that 
some  poison  is  present,  usually  removable  by  another  treatment 
with  bromine  water.  Following  the  estimation  of  oxygen  comes 
that  of  carbon  monoxide  with  cuprous  chloride  either  acid  or 
ammoniacal,  preferably  acid  unless  hydrogen  is  to  be  absorbed 
by  palladium.  Two  cuprous  chloride  pipettes  must  be  used  in 
series,  the  second  one  containing  almost  fresh  reagent.  The  resi- 
due from  this  absorption  consists  of  hydrogen,  hydrocarbons  of 
the  paraffine  series  and  nitrogen.  The  hydrogen  may  be  ab- 
sorbed by  palladium  as  outlined  in  this  chapter  but  it  is  more 
common  practice  to  estimate  the  hydrogen  and  hydrocarbons 
by  combustion.  The  methods  are  discussed  in  the  next  chapter. 


CHAPTER  IV 

EXPLOSION  AND  COMBUSTION  METHODS  FOR 

HYDROGEN,  METHANE,  ETHANE 

AND  CARBON  MONOXIDE 

1.  Available  Methods. — Hydrogen  and  carbon  monoxide  may 
be  estimated  by  absorption  as  indicated  in  the  preceding  chapter. 
They  may  also  be  estimated  after  oxidation  to  water  or  carbon 
dioxide.  There  are  no  satisfactory  absorbents  for  methane  and 
ethane  and  so  these  gases  are  always  estimated  indirectly  after 
oxidation.  The  oxidizing  agent  may  be  gaseous  oxygen  and  the 
reaction  may  be  violent  as  in  explosion  methods  or  it  may  be 
quiet  combustion.  There  may  even  be  combustion  of  hydrogen 


•Extrathtck 
Wall 


Platinum 

Wire, 
Fused  in-- 


Stop  Cock,  2mm. 
Bore 

*3 mm.  Infernal 

Diameter 

FIG.  10. — Detail  of  explosion  pipette. 

and  carbon  monoxide  with  the  aid  of  a  catalyzer  in  the  presence 
of  methane  which  remains  unchanged.  The  oxidizing  agent  may 
also  be  an  oxide,  especially  copper  oxide,  and  here  again  there 
may  be  fractional  combustion.  The  most  rapid  method  and 
the  one  most  frequently  used  is  that  of  explosion. 

2.  Apparatus  for  Explosion  Analysis. — The  analysis  by  ex- 
plosion is  carried  out  in  a  stout  glass  vessel  provided  with  elec- 
tric connections  across  whose  terminals  a  spark  may  be  passed 
to  cause  the  explosion.  The  shape  and  dimensions  of  the  appa- 
ratus may  vary.  The  form  which  has  given  good  satisfaction 

43 


44  GAS  AND  FUEL  ANALYSIS 

in  the  gas  laboratory  at  the  University  of  Michigan  for  a  number 
of  years1  is  shown  in  Fig.  10.  It  is  a  modification  of  the  Hempel 
pipette  and  differs  from  it  principally  in  the  arrangement  of  the 
electric  terminals  and  in  the  incorporation  of  an  explosion  guard 
in  the  stand. 

In  the  older  forms  of  pipette  the  explosion  was  induced  by  a 
spark  made  to  jump  a  gap  between  two  platinum  wires  sealed 
through  the  glass  of  the  narrowed  upper  part  of  the  bulb.  When 
the  interior  of  the  bulb  became  wet  as  frequently  happened  the 
electric  current  would*  sometimes  travel  around  the  wet  wall 
instead  of  sparking  across  the  gap,  and  it  was  not  possible  to 
obtain  an  explosion.  Gill2  modified  the  bulb  by  introducing  one 
of  the  wires  through  a  ground  glass  joint  at  the  bottom  of  the 
pipette.  This  was  a  valuable  modification  because  it  made 
the  creeping  distance  so  long  that  the  spark  was  compelled  to 
jump  the  gap,  but  the  ground  glass  was  difficult  to  keep  tight. 
The  form  here  described  introduces  the  wire  from  the  bottom  but 
adopts  a  simple  method  of  sealing  which  is  very  satisfactory. 
The  lower  wire  which  should  be  stiff  (and  may  be  of  nickel  about 
1  mm.  in  diameter)  is  pushed  through  the  open  lower  end  of 
the  pipette  and  sealed  by  sucking  molten  sealing  wax  into  the 
pipette  almost  to  the  level  of  the  tee.  As  the  sealing  wax 
hardens  the  wire  may  be  moved  to  adjust  the  spark  gap  to  the 
desired  dimensions.  No  difficulty  has  been  experienced  in 
making  this  joint  tight.  The  explosion  pipette  and  its  stand 
are  shown  in  Fig.  11.  The  bulb  is  enclosed  in  a  box  open  at 
the  top  and  with  a  plate  glass  window  in  front,  so  that  the 
operator  can  observe  the  explosion  in  perfect  safety.  The  bot- 
tom of  this  box  has  an  irregular  opening  sawed  in  it  so  that  the 
pipette  as  shown  in  Fig.  10  may  be  lowered  into  place.  The  bulb 
sits  in  a  cup  shaped  hollow  of  the  shelf  which  may  be  padded 
with  wet  asbestos  paper  if  necessary  to  make  it  fit  well. 

The  weight  of  the  mercury  renders  other  fastening  for  the  bulb 
unnecessary  but  the  capillary  is  fastened  to  the  rib  behind  it  by 
a  loop  of  fine  copper  wire  passing  through  holes  drilled  in  the  rib. 
The  strain  of  the  rubber  tube  filled  with  mercury  is  taken  off  the 
glass  tee  by  a  ring  below  the  shelf  into  which  the  rubber  tube  is 

1  White  and  Campbell,  J.  Am.  Chem.  Soc.,  27,  734  (1905). 

2  J.  Am.  Chem.  Soc.,  17,  771  (1895). 


EXPLOSION  AND  COMBUSTION  METHODS 


45 


wedged  firmly  by  a  split  cork.  The  rack  for  the  levelling  bottle 
is  higher  than  the  tee  of  the  pipette  so  that  when  the  bottle  is  in 
the  rack  the  mercury  in  the  rubber  tube  is  under  pressure  whereas 
if  the  mercury  bottle  were  sitting  on  the  base  of  the  stand  there 
would  be  a  partial  vacuum  within  the  rubber  tube.  This  may 
seem  immaterial,  but  it  must  be  remembered  that  all  rubber  is 
porous  and  that  bubbles  of  air  sucked  into  the  rubber  tube  are 
certain  to  make  their  way  up  into  the  pipette  and  be  measured 


FIG.  11. — Explosion  pipette  and  stand  with  protecting  screen. 

as  part  of  the  gas  in  it.  Fine  copper  wires  soldered  to  the  elec- 
trode terminals  of  the  pipette  pass  to  the  binding  posts  on  the 
stand.  The  fine  platinum  electrode  is  liable  to  be  cut  if  it  is 
bent  back  and  forth  where  it  is  sealed  through  the  glass  and  to 
protect  it  the  copper  wire  from  the  upper  electrode  is  brought 
smoothly  up  to  the  capillary  and  tied  there  firmly  with  thread. 
The  design  of  the  stand  is  such  that  if  a  bulb  breaks  a  new  bulb 
may  be  inserted  without  trouble  if  it  has  even  approximately  the 
dimensions  gf  the  old  one.  The  method  of  connecting  this  pipette 
to  the  burette  and  of  transferring  the  gas  is  the  same  as  for  other 


46  GAS  AND  FUEL  ANALYSIS 

pipettes.  This  pipette  is  filled  with  mercury,  since  under  the 
high  pressure  developed  the  solubility  of  the  gases  in  water 
becomes  large  enough  to  cause  appreciable  error.  An  induction 
coil  capable  of  giving  a  half  inch  spark  together  with  its  bat- 
tery is  necessary.  A  coil  giving  a  large  spark  such  as  is  given 
by  the  automobile  sparkers  is  much  better  than  a  coil  giving  a 
thin  high  voltage  spark. 

3.  Manipulation  in  Explosion  Analysis. — In  the  explosion  proc- 
ess a  sample  of  gas  previously  freed  from  carbon  dioxide,  oxygen, 
unsaturated  hydrocarbons  and  usually  carbon  monoxide  is  drawn 
into  the  burette  and  measured.  Its  volume  may  vary  from  8.0 
c.c.  with  pure  methane  to  50  c.c.with  gases  containing  high  per- 
centages of  nitrogen.  Air  sufficient  to  fill  the  burette  is  then 
drawn  in.  The  burette  is  connected  to  the  pipette  as  usual, 
care  being  taken  to  have  the  rubber  connections  in  good  condition 
and  firmly  wired,  and  the  mixture  is  passed  into  the  explosion 
pipette,  the  water  of  the  burette  being  run  over  through  the  cap- 
illary of  the  pipette  until  the  capillary  is  full.  This  water  in  the 
capillary  acts  as  a  cushion,  preventing  the  force  of  the  explosion 
from  blowing  up  the  rubber  connections.  The  gas  in  the 
explosion  pipette  is  brought  to  atmospheric  pressure  by  means 
of  the  levelling  bottle,  the  stopcock  is  closed,  and  the  levelling 
bottle  replaced  in  its  rack.  It  is  advisable  to  shake  the  pipette  to 
ensure  thorough  mixing  of  the  gases,  for  diffusion  proceeds  some- 
what slowly.  The  gas  is  exploded  by  a  spark  from  the  induction 
coil.  If  the  gas  consists  mainly  of  hydrogen  there  is  usually 
no  visible  flame  although  a  slight  tremor  of  the  mercury  may  be 
observed.  If  the  gas  contains  much  hydrocarbon  a  flash  of  flame 
may  usually  be  seen.  It  is  not  advisable  to  spark  the  mixture 
more  than  a  second  as  some  nitrogen  will  unite  with  the  oxygen 
at  the  temperature  of  the  spark  forming  oxides  of  nitrogen  with 
decrease  of  volume  and  erroneous  results.  The  explosion  com- 
pleted, the  gas  is  again  brought  to  atmospheric  pressure  by  means 
of  the  levelling  bottle,  and  then  brought  back  into  the  burette  and 
measured.  If  there  has  been  marked  contraction,  the  next  step 
is  to  pass  the  gas  into  caustic  solution  and  determine  if  there 
has  been  formation  of  carbon  dioxide. 

If  the  decrease  in  volume  after  explosion  was  less  than  12 
c.c.  it  is  almost  certain  that  the  explosion  was  incomplete.  If 


EXPLOSION  AND  COMBUSTION  METHODS  47 

there  was  no  decrease  in  volume  it  is  not  safe  to  assume  that  no 
combustible  gas  was  present,  for  it  may  have  been  present  in  such 
a  small  proportion  that  the  mixture  was  not  explosive.  The 
proper  procedure  in  either  case  is  to  add  about  10  c.c.  of  pure 
hydrogen  made  by  the  action  of  caustic  soda  on  metallic  alumi- 
nium and  explode  a  second  time.  The  addition  of  this  amount 
of  hydrogen  ensures  complete  explosion.  After  allowance  for 
the  contraction  due  to  the  added  hydrogen,  the  composition  of 
the  original  gas  may  be  calculated  as  explained  later. 

It  is  advisable  to  determine  roughly  the  amount  of  oxygen 
remaining  after  the  explosion  so  that  there  may  be  no  doubt 
that  an  excess  was  present. 

4.  Oxidation  of  Nitrogen  as  a  Source  of  Error. — Almost  all 
technical  gases  contain  nitrogen  as  do  also  commercial  forms  of 
oxygen.  Bunsen  first  noted  that  nitrogen  and  oxygen  react  at 
the  temperature  of  the  electric  spark  or  of  an  explosion  flame  to 
form  small  amounts  of  various  oxides  of  nitrogen  whose  volume 
is  less  than  that  of  the  reacting  gases  and  which  combine  with 
caustic.  The  formation  of  oxides  of  nitrogen  leads,  therefore,  to 
an  erroneously  high  contraction  after  explosion  and  to  an  errone- 
ously high  figure  for  CO2  due  to  explosion.  The  error  is  discussed 
more  fully  in  Chapter  VI  on  Exact  Gas  Analysis  but  it  cannot  be 
altogether  neglected  in  technical  work.  The  error  increases  with 
higher  flame  temperatures  and  the  simplest  way  to  keep  it  within 
reasonable  limits  is  to  dilute  the  reacting  gases  with  some  inert 
gas  such  as  nitrogen  or  excess  of  oxygen.  The  volume  of  the 
gases  participating  in  the  explosion  (combustible  gas  +  theoret- 
ical volume  oxygen)  should  be  from  one-third  to  one-fifth  that 
of  the  non-exploding  gases  (nitrogen  +  excess  oxygen).  It  will 
be  seen  that  12  c.c.  H2+  6  c.c.  O2  require  to  be  diluted  with  from 
54  to  90  c.c.  nitrogen  or  oxygen  and  that  8  c.c.  CH4  -f-  16  c.c. 
O2  require  at  least  72  c.  c.  of  diluting  gases. 

The  explosion  of  large  samples  of  gas  mixed  with  commercial 
oxygen,  a  method  proposed  by  Hinman  and  endorsed  by  Gill,1 
involves  much  greater  danger  of  blowing  up  the  pipette  and  be- 
cause of  the  higher  temperature  of  explosion,  tends  to  cause 
a  larger  formation  of  oxides  of  nitrogen  from  the  nitrogen 
necessarily  present. 

1  J.  Am.  Chem.  Soc.,  17,  987  (1895). 


48  GAS  AND  FUEL  ANALYSIS 

5.  Accuracy  of  Explosion  Methods. — The  necessity  of  diluting 
the  exploding  gases  to  avoid  oxidation  of  nitrogen  restricts  the 
size  of  a  sample  of  a  rich  gas  like  illuminating  gas  to  about  10 
c.c.     With  this  small  sample  each  0.1  c.c.  error  in  reading  means 
1.0  per  cent.     A  greater  accuracy  can  therefore  not  be  expected 
except  by  averaging  a  number  of  analyses.     It  may  be  considered 
safe  to  rely  upon  a  single  analysis  for  the  various  gases  deter- 
mined by  absorption,  but  explosion  analyses  should  always  be 
made  in  duplicate.     The  main  portion  of  the  gas  after  the 
absorption  should  be  stored  in  a  gas  holder  to  be  drawn  upon  for 
subsequent  check  analyses. 

6.  Hydrogen  by  Explosion. — If  hydrogen  is  the  only  com- 
bustible gas  taking  part  in  the  explosion  its  volume  may  be 
calculated  from  the  contraction  after  explosion  according  to 
the  following  equation: 

2H2+O2  =  2H2O 
2+1  =2orO 

Expressed  in  volumes  this  means  that  two  volumes  of  hydrogen 
combine  with  one  volume  of  oxygen  to  form  two  volumes  of 
water  vapor.  Since,  however,  the  gas  after  explosion  cools 
again  to  the  temperature  of  the  burette  water  and  is  the  same 
as  before  explosion,  and  since  it  was  saturated  with  water 
before  explosion,  the  additional  water  formed  must  all  condense. 
For  our  purposes,  therefore,  two  volumes  of  H2  react  with  one 
volume  of  02  with  complete  disappearance  of  the  reacting  gases. 
Under  these  circumstances  when  hydrogen  is  the  only  exploding 
gas,  two-thirds  of  the  resulting  contraction  will  be  the  volume 
of  the  hydrogen  exploded. 

7.  Hydrogen  and  Methane  by  Explosion. — Methane  combines 
with  two  volumes  of  oxygen  to  form  carbon  dioxide  and  water 
according  to  the  following  equation: 

CH4+2O2  =  CO2+2H20 
1+2      =1+0 

The  volumetric  relations  are  expressed  by  the  figures  of  the 
equation,  one  volume  of  methane  uniting  with  two  of  oxygen 
to  form  one  volume  of  carbon  dioxide,  ami  two  of  water  vapor 


EXPLOSION  AND  COMBUSTION  METHODS  49 

which  condense  and  disappear  as  explained  in  the  preceding 
paragraph.  The  result  of  the  explosion,  therefore,  is  that  there 
is  a  contraction  of  two  volumes  for  every  one  volume  of  methane 
and  the  formation  of  a  volume  of  carbon  dioxide  equal  to  the 
methane. 

It  is  possible  to  determine  the  proportion  of  hydrogen  and 
methane  present  in  a  gas  mixture  by  explosion  with  air.  The 
volume  of  carbon  dioxide  resulting  from  the  explosion  equals 
the  volume  of  the  methane.  The  contraction  due  to  the  methane 
is  twice  the  volume  of  the  methane  and  the  difference  between 
this  contraction  in  volume  and  the  total  contraction  is  the 
contraction  due  to  the  explosion  of  hydrogen.  In  accordance 
with  the  preceding  section  two-thirds  of  this  contraction  is 
hydrogen.  The  following  example  will  serve  as  an  illustration 
of  the  method  of  calculation. 


Sample  of  illuminating  gas 99 . 5      c.c. 

Volume  after  absorption  of  CO2,  CnH2n,  O2,  CO 85 . 2 

Sample  for  explosion 10 . 3 

Air  to 97.6 

After  explosion,  volume 80 . 1 

Contraction 17.5 

After  KOH,  volume 74 . 9 

Vol.  CO2  formed 5.2 

After  phosphorus,  volume 69 . 4 

Vol.  excess  oxygen 5.5 

Calculation  5.2  c.c.  CO2  =  5.2  c.  c.  CH4 

Contraction  due  to  5.2  c.c.  CH4  =  2X5.2  =  10.4 
Contraction  due  to  hydrogen  =17.5— 10. 4  =  7.1 
Hydrogen      =    2/3X7.1=4.7 
Vol.     CH4     =    5.2 
Vol.        H2     =    4.7 
Vol.  N,bydiff.  0.4 

10.3 


Per  cent. 


Percent.    H2    _4.7X  -39.0 


Percent,   N2    =0.4X^^^=3.3 


50  GAS  AND  FUEL  ANALYSIS 

The  ratio  of  exploding  to  non-exploding  gases  in  the  above 
illustration  may  be  calculated  as  follows: 

Exploding  gases  5.2  c.c.  CH4-fl0.4  c.c.  O»  =  15.6 
4.7c.c.     H2+2.35  c.c.  O2=  7.05 


Exploding  gases  22 . 65 

Non-exploding  gases  97 . 6 — 22 . 65  =  74 . 95 

exploding  gases        22.65        1 
non-exploding  gases     74.95  ~~  3.3 

The  excess  of  oxygen  is  calculated  from  the  volume  of  an 
taken  for  explosion,  =97.6  —  10.3  =  87.3  c.c.  air  with  20.9  pel 
cent.  O2=  18.24  c.c.  O2  available.  Used  for  combustion) 
as  above,.  10.4+2.35  =  12.75  c.c.  Excess  oxygen  =  18.24- 
12.75  =  5.49  c.c.,  which  checks  with  the  5.5  c.c.  found  by  direct 
experiment. 

8.  Carbon  Monoxide,  Hydrogen  and  Methane  by  Explosion.  — 
The  composition  of  a  gas  mixture  containing  CO,  H2,  and  CH< 
may  be  determined  by  a  single  explosion  ii  in  addition  to  the 
contraction  and  C02  the  oxygen  used  in  the  explosion  is  also 
determined. 

There  are  various  methods  of  calculation,  that  given  by 
Noyes  and  Shepherd1  being  as  follows: 

1.  Gas  taken  =CH4+CO  +  H2+N2 

2.  Contraction  =2CH4+iCO+fH2 

3.  Oxygen  consumed  =2CH4+JCO  +  fH2 

4.  CO2iormed  =CH4+CO 

Hence      H2  =  Contraction  —  O2  consumed. 
CO  =  |  (2CO2+|H2-02  consumed) 
CH4  =  CO2-CO 

N2  =  Total  gas-(H2+CO+CH4). 

The  oxygen  consumed  is  calculated  by  determining  the  residual 
oxygen  and  deducting  this  from  the  volume  of  oxygen  introduced 
as  air  whose  percentage  of  oxygen  is  assumed  to  be  20.9. 

This  method  is  more  rapid  than  the  usual  one  in  which  the 
CO  is  absorbed  by  Cu2Cl2,  and  it  has  no  systematic  errors, 
provided  the  dilution  is  great  enough  to  avoid  oxidation  oi 
nitrogen.  It  will,  except  in  expert  hands,  be  found  less  reliable 

1  J.  Am.  Chem.  Soc.  20,  345  (1898). 


EXPLOSION  AND  COMBUSTION  METHODS  51 


than  the  usual  method  of  absorption  of  CO  and  explosion  of  H2 
and  CH4  because  each  value  calculated  is  dependent  on  the 
accuracy  of  three  successive  operations  instead  of  two. 

9.  Quiet  Combustion  of  a  Mixture  of  Oxygen  and  Combust- 
ible Gas. — Various  attempts  have  been  made  to  do  away  with 
the  explosion  pipette  by  causing  the  gas  to  burn  gradually. 
Coquillion1  in  1876  proposed  to  estimate  small  amounts  of 
hydrocarbons  in  the  air  from  mines  by  placing  within  a  pipette 
a  spiral  of  platinum  or  palladium  wire.  The  mine  air  was  in- 
troduced into  the  pipette,  the  spiral  was  to  be  heated  to  redness 
and,  the  amount  of  combustible  gas  being  below  the  explosive 
ratio,  the  hydrocarbons  were  to  be  gradually  burned.  He 
recommended  that  for  technical  gases  where  there  was  danger 
of  explosion  the  platinum  spiral  be  placed  in  a  small  bulb  blown 


FIG.  12. — Quartz  combustion  tube  with  platinum  spiral. 

in  the  capillary  tube  between  the  burette  and  pipette.  The 
mixture  of  gas  and  air  was  measured  in  the  burette,  and  then 
passed  through  the  capillary  over  the  glowing  spiral.  The 
capillary  tube  was  supposed  to  be  adequate  to  prevent  the 
explosion  from  flashing  back  into  the  burette.  Hempel2  has 
improved  this  latter  apparatus  by  placing  the  platinum  spiral 
in  a  quartz  tube  between  two  glass  capillary  tubes.  His  arrange- 
ment as  modified  by  the  author  is  shown  in  Fig.  12  where  AB 
represents  a  tube  of  transparent  quartz  about  4  mm.  internal 
diameter  and  125  mm.  long,  at  each  end  of  which  are  glass  cap- 
illary tees  connected  to  it  by  rubber  tubing.  Through  each  tee 
runs  a  stout  nickel  wire  connected  by  a  spiral  of  fine  platinum 
wire.  The  nickel  wires  are  sealed  into  the  glass  capillaries  by 
sealing  wax  drawn  into  the  enlarged  ends  of  the  capillaries.  The 
apparatus  may  therefore  be  readily  repaired  if  the  platinum 

1  Comptes  rendus,  83,  394;  84,  458  and  1503. 

2  Zeit.  angewandt.  Chem.,  25,  1841  (1912). 


52  GAS  AND  FUEL  ANALYSIS 

wire  becomes  burned  out.  The  nickel  wires  should  be  so  large 
that  they  almost  fill  the  capillary  tube  which  should  be  of  about 
1  mm.  internal  diameter.  They  will  then  not  be  heated  per- 
ceptibly by  the  passage  of  an  electric  current  sufficient  to  heat 
the  platinum  wire  to  redness  and  will  by  their  cooling  action 
help  to  prevent  the  explosion  from  flashing  back  into  the  gas 
burette.  If  the  mixture  of  gas  and  air  is  passed  slowly  over  the 
platinum  spiral  the  temperature  will  not  rise  above  a  fair  red 
heat  and  there  will  be  little  danger  of  formation  of  oxides  of 
nitrogen,  hence  there  is  no  need  of  diluting  the  gases  with  so 
much  air  as  is  necessary  in  the  explosion  process  and  therefore  a 
larger  sample  of  gas  may  be  used.  It  is  not  safe,  however,  to 
take  a  large  sample  of  gas  and  dilute  it  with  pure  oxygen,  for  the 
capillary  tube  cannot  be  relied  upon  to  prevent  an  explosion 
flashing  back  into  the  burette  when  a  very  explosive  mixture  is 
used. 

The  inaccuracy  of  the  usual  explosion  methods  led  Dennis 
and  Hopkins1  to  devise  a  process  of  combustion  whereby  a 
large  sample  of  gas  might  be  quietly  burned  in  pure  oxygen. 
The  combustion  pipette  consists  of  a  pipette  such  as  is  used  for 
phosphorus  with  its  second  bulb  cut  off  and  a  levelling  bottle 
for  mercury  connected.  The  ignition  wire  in  the  form  of  a 
platinum  coil  or  grid  is  placed  within  the  pipette  immediately 
under  the  gas  inlet  and  connected  to  two  heavy  wires  which, 
insulated  from  each  other,  pass  through  the  rubber  stopper  at 
the  bottom  of  the  pipette  and  are  fastened  to  binding  posts. 
The  diameter  and  length  of  the  platinum  ignition  wire  must  be 
chosen  with  reference  to  the  electric  circuit  so  that  it  will  be 
easily  heated  to  redness  and  its  temperature  controlled  without 
the  need  of  cumbrous  rheostats.  The  conducting  wires  within 
the  pipette  may  be  of  platinum  or  one  of  the  non-rusting  nickel- 
chromium  alloys  and  should  be  at  least  1  mm.  in  diameter. 

The  manipulation  is  as  follows.  The  full  volume  of  gas 
remaining  after  absorption  of  oxygen,  consisting  of  CO,  H2, 
CH4  and  N2  is  transferred  to  the  combustion  pipette  and  a 
clamp  is  screwed  onto  the  rubber  connecting  tube  at  the  tip  of 
the  burette  so  that  the  pipette  may  be  disconnected  from  the 
burette.  The  burette  is  filled  with  oxygen  free  from  CO2  and 

1  /.  Am.  Chem.  Soc.,  21,  398  (1899). 


EXPLOSION  AND  COMBUSTION  METHODS  53 

of  known  purity  and  reconnected  to  the  pipette,  but  the  stop- 
cock of  the  burette  is  kept  closed.  The  levelling  bottle  of  the 
pipette  is  placed  at  such  a  height  that  the  gas  in  the  pipette  is 
under  slightly  diminished  pressure  and  the  electric  ignition  wire 
brought  to  incandescence.  The  stopcock  on  the  burette  is 
now  opened  and  a  slow  stream  of  oxygen  passed  into  the  pipette. 
A  slight  flash  is  usually  noticeable  as  ignition  takes  place  and 
the  platinum  wire  glows  more  brightly  so  that  it  may  be  necessary 
to  interpose  more  resistance  in  the  heating  circuit.  The  volume 
of  gas  in  the  pipette  may  either  increase  or  decrease  and  the 
height  of  the  levelling  bottle  must  be  varied  accordingly.  It  is 
usually  necessary  to  periodically  increase  the  external  resistance 
to  prevent  the  platinum  wire  from  burning  out  as  the  hydrogen 
originally  present  gives  way  to  water  vapor.  After  the  oxygen 
is  all  passed  into  the  pipette,  the  current  is  interrupted,  the  gases 
allowed  to  cool  and  the  CO,  H2  and  CH4  determined  as  in  §  8. 

The  great  advantage  of  this  process  lies  in  the  large  sample 
and  the  consequent  diminution  of  the  error  of  observation.  It 
requires  a  special  pipette,  which  is,  however,  easily  constructed, 
a  source  of  electric  current  and  a  controlling  rheostat.  The 
manipulation  is  somewhat  complicated  and  it  has  been  the 
author's  experience  that  novices  usually  wish  that  nature  had 
provided  them  with  an  extra  pair  of  hands.  The  error  due  to 
oxidation  of  nitrogen  has  been  found  by  the  author1  to  be  fully 
as  large  in  this  process  as  in  the  explosion  process.  The  subject 
is  discussed  more  fully  in  Chapter  VI.  Hempel2  also  reports 
unfavorably  on  this  process  on  account  of  the  formation  of  oxides 
of  nitrogen  when  combustion  is  continued  long  enough  to  ensure 
oxidation  of  all  the  methane. 

10.  Fractional  Combustion  with  Palladinised  Asbestos. — The 
well  known  power  of  palladium  to  bring  about  the  union  of  hy- 
drogen and  oxygen  at  low  temperature  has  long  been  made  use 
of  as  a  means  of  separating  hydrogen  from  methane.  The  use 
of  palladinised  asbestos  is  due  to  Winkler.  The  asbestos  is 
prepared  by  soaking  a  small  amount  of  selected  long  fibered 
asbestos  in  a  concentrated  solution  of  palladous  chloride  prepared 
according  to  §  7  of  Chapter  III.  The  fibers  are  to  be  kept  as 

1J.  Am.  Chem.  Soc,  23,  477  (1901). 
*Zeit.  Angewandt.  Chem.,  25,  1841  (1912). 


54  GAS  AND  FUEL  ANALYSIS 

nearly  parallel  as  possible  and  after  saturation  are  to  be  dried 
and  ignited  at  a  very  dull  red  heat  when  the  chloride  will  de- 
compose leaving  the  fibers  coated  with  metallic  palladium  and 
possibly  palladous  oxide.  A  bundle  of  two  or  three  of  these 
single  fibers  about  an  inch  long  is  introduced  into  the  end  of  a 
straight  capillary  glass  tube  about  1  mm.  internal  diameter  and 
eight  inches  long,  and  brought  to  the  middle  of  the  capillary  by 
suction  on  the  opposite  end  of  the  tube.  A  drop  of  water  on 
the  asbestos  makes  it  move  more  freely.  The  capillary  is  then 
to  be  dried  and  bent  to  the  usual  form  for  connecting  the  burette 
and  pipette. 

In  manipulation  20  or  30  c.c.  of  gas  freed  from  C02,  CnH2n 
and  usually  CO  is  mixed  with  an  excess  of  air  and  passed  through 
the  capillary  tube  containing  the  palladinised  asbestos  into  a 
pipette  containing  water.  If  the  asbestos  is  very  active,  com- 
bustion may  begin  without  external  heat  but  to  make  certain 
the  tube  is  heated  with  a  small  gas  flame  or  alcohol  lamp.  It  is 
not  necessary  to  heat  the  tube  to  redness.  A  spark  frequently 
appears  at  the  end  of  the  asbestos  filament  when  the  combustible 
gas  first  strikes  it.  This  is  a  sign  that  the  gas  is  passing  too 
rapidly  and  the  speed  must  be  decreased  until  the  spark  disap- 
pears. Otherwise  some  methane  will  be  burned.  The  gas  is 
passed  back  and  forth  through  the  capillary  twice  and  then  drawn 
back  into  the  burette  and  the  volume  measured.  If  hydrogen 
alone  has  been  burned  two-thirds  of  the  contraction  will  be  the 
volume  of  the  hydrogen  as  explained  in  §  6.  Carbon  monoxide 
will  burn  as  well  as  hydrogen  in  this  process  and  where  both 
were  present,  it  will  be  necessary  to  determine  the  carbon  dioxide 
formed  in  addition  to  the  contraction.  The  calculations  follow 
from  the  equations: 

2CO+02  =  2C02 

2+1       =2  Contraction  =  i CO  or 

2H2+O2  =  2H2O 

2+1    =0  Contraction  =  |H2 

ThereforeC02  =  CO 

Total  contraction  =  JCO+|H2 
H2  =  f  (contraction— JCO) 


EXPLOSION  AND  COMBUSTION  METHODS  55 

This  method  is  accurate  provided  the  palladinised  asbestos 
is  dry  and  active  and  the  proper  temperature  is  maintained. 
It  requires  care  to  prevent  any  drops  of  water  from  getting  into 
the  capillary.  If  this  happens  when  the  capillary  is  cold  the 
thread  of  asbestos  becomes  wet  and  must  be  dried  thoroughly 
before  it  is  active.  If  a  drop  of  water  gets  into  the  capillary 
while  it  is  hot  the  glass  tube  cracks.  Very  little  attention  has 
been  paid  to  the  possibility  of  small  amounts  of  foreign  gases 
rendering  the  palladium  catalyzer  inactive,  but  from  the  elaborate 
precautions  which  are  necessary  to  keep  the  platinum  contact 
substance  active  in  the  sulphuric  acid  manufacture  it  is  evident 
that  this  possibility  should  not  be  ignored.  The  capillary  tube 
should  never  be  heated  to  redness  on  account  of  danger  of  burn- 
ing methane.  The  combustible  gases  are  diluted  largely  with 
air  to  avoid  too  intense  combustion  and  also  to  avoid  an  ex- 
plosion of  the  main  body  of  the  gas  which  might  be  propagated 
through  the  capillary  if  the  gas  mixture  were  too  rich.  Dis- 
astrous explosions  have  been  known  to  result  from  an  attempt 
to  burn  mixtures  of  hydrogen  and  oxygen  in  this  manner.  The 
combined  volumes  of  hydrogen  and  carbon  monoxide  in  the 
sample  taken  for  analysis  should  not  be  over  20  c.c.  and  the 
volume  after  dilution  with  air  should  be  almost  100  c.c.  This 
method  has  been  investigated  by  Nesmjelow1  who  emphasizes 
the  danger  of  burning  methane  if  the  gases  are  passed  through 
the  capillary  at  a  rate  faster  than  one  liter  per  hour.  Hempel2 
has  recently  reported  the  results  of  a  study  of  this  process  and 
finds  that  to  obtain  accurate  results  the  temperature  of  the 
capillary  must  not  rise  over  400°  C.  and  that  the  gas  must  be 
passed  at  a  speed  of  not  over  100  c.c.  in  eight  minutes.  He  rec- 
ommends, as  a  method  of  temperature  control,  that  the  portion 
of  the  capillary  to  be  heated  rest  in  a  brass  trough  which  in  the 
middle  is  thickened  sufficiently  to  contain  a  hole  deep  enough 
for  a  thermometer  bulb.  In  default  of  a  thermometer  a  glass 
tube  sealed  at  the  bottom  and  containing  a  little  mercury  may 
be  inserted  in  the  hole.  The  boiling  of  the  mercury  (358° 
C.)  indicates  when  a  sufficiently  high  temperature  has  been 
reached. 

1  Zeit.  Anal.  Chem.,  48,  232  (1909). 
*Zeit.  Angewandt.  Chem.,  25,  1841  (1912). 


56  GAS  AND  FUEL  ANALYSIS 

11.  Fractional  Combustion  with  Copper  Oxide. — The  com- 
bustion of  carbon  compounds  of  all  sorts  through  contact  with 
hot  copper  oxide  has  been  a  method  long  employed  by  organic 
chemists.  Campbell1  first  utilized  the  principle  of  fractional 
combustion  in  gas  analysis  and  determined  accurately  the  mini- 
mum combustion  temperature  for  various  gases  both  with  copper 
oxide  alone  and  with  palladinised  copper  oxide.  His  values 
are  as  follows: 


Gas 

Initial  combustion  point 

Pure  CuO                            Pd.-CuO 

H2                            

175-180°  C. 
100-105°  C. 
315-325°  C. 
270-280°  C. 
320-330°  C. 
No  combustion  at  455°  C. 

80-85°  C. 
100-105°  C. 
240-250°  C. 
220-230°  C. 
270-280°  C. 

CO 

C2H4  
C3H6                  

C4H8  (Iso) 

CH4  

Jaeger2  first  proposed  a  convenient  scheme  for  utilizing  this 
principle  in  ordinary  gas  analysis  and  the  method  usually  bears 
his  name.  He  takes  advantage  of  the  wide  difference  in  the 
ignition  point  of  CO  and  H2  as  compared  with  CH4  to  separate 
the  two  gases  by  fractional  combustion.  His  method  with  some 
modifications  which  the  author  has  found  desirable  is  as  follows : 

The  combustion  tube  shown  at  A  in  Fig.  13  is  of  hard  Jena 
glass  or  preferably  transparent  quartz  and  has  an  internal 
diameter  of  about  10  mm.  and  a  length  of  200  mm.  It  is  filled 
throughout  its  middle  100  mm.  with  granulated  copper  oxide 
kept  in  place  by  wads  of  asbestos  fiber.  The  open  ends  of  the 
tube  are  closed  by  elbows  of  glass  capillary  tubing  which  slip 
within  each  end  of  the  combustion  tube  as  far  as  the  asbestos 
wads  and  are  held  in  place  by  rubber  tubing  fitting  tightly  over 
the  end  of  the  combustion  tube  and  also  over  the  glass  capillary. 
The  asbestos  shield  shown  in  section  at  B  and  in  elevation  at  C 
sits  like  a  saddle  over  the  middle  portion  of  the  tube  and  keepa 
the  heat  from  the  rubber  connections  during  combustion. 
The  combustion  gases  pass  out  the  perforations  shown  in  the 
top  of  the  shield.  A  thermometer  standing  in  the  tube  of  the 

1  Am.  Chem.  Jour.,  17,  688  (1895). 
*Jour.Gasbeleucht,  41,764  (1898). 


EXPLOSION.  AND  COMBUSTION  METHODS  . 


57 


shield  with  its  bulb  touching  the  combustion  tube  indicates 
the  temperature  at  which  hydrogen  is  being  burned. 

The  whole  volume  of  the  gas  from  which  C02,  CnH2n  and  O2 
have  been  removed  is  used  for  the  analysis.  The  copper  oxide 
tube  is  connected  to  the  burette  on  one  side  and  on  the  other  to 
a  phosphorus  pipette  which  has  been  previously  filled  with  air 
and  now  contains  nitrogen.  This  nitrogen  is  allowed  to  flow 
through  the  combustion  tube  and  out  into  the  air  through  the 
burette  stopcock  flushing  out  the  air  in  the  tube  and  rendering 


Jl. 


FIG.  13. — Quartz  combustion  tube  filled  with  copper  oxide. 

unnecessary  the  troublesome  correction  involved  in  Jaeger's 
original  method.  The  nitrogen  is  all  driven  out  of  the  phos- 
phorus pipette,  and  the  water  in  it  blown  to  a  mark  arbitrarily 
fixed  on  the  capillary  stem  of  the  pipette  and  the  burette  stop- 
cock turned  so  that  connection  with  the  outside  air  is  shut  off, 
the  burette  also  remaining  closed.  The  gas  burner  under  the 
combustion  tube  is  lighted  and  adjusted  so  that  the  thermometer 
inserted  in  the  jacket  and  resting  on  the  combustion  tube  shows 
about  250°  C.  The  expanding  nitrogen  in  the  combustion 
tube  is  free  to  pass  into  the  phosphorus  pipette.  When  the 


58  GAS  AND  FUEL  ANALYSIS 

combustion  tube  is  hot,  the  burette  stopcock  is  opened  and 
the  gas  passed  slowly  into  the  phosphorus  pipette  and  back 
again  so  that  it  has  all  been  exposed  twice  to  the  action  of  the 
copper  oxide.  A  few  cubic  centimeters  of  the  gas  are  again 
passed  into  the  phosphorus  pipette,  the  burette  stopcock  is 
closed  and  the  flame  removed.  If  the  combustion  tube  is  of 
glass  it  must  be  slowly  cooled  to  room  temperature  but  if  it  is 
of  quartz  it  may  be  sprayed  with  water  or  wrapped  with  a  wet 
cloth  until  it  again  reaches  room  temperature.  As  the  tube 
cools  there  is  sucked  back  from  the  pipette  some  of  the  gas 
purposely  placed  there  and  when  it  is  thought  that  the  tube 
has  reached  room  temperature  the  liquid  of  the  pipette  is  again 
brought  to  the  mark  in  the  capillary  which  was  used  at  the  com- 
mencement of  the  test.  If  after  adjustment  has  been  made  the 
water  of  the  pipette  continues  to  rise  in  the  capillary  it  is  proof 
that  the  combustion  tube  has  not  yet  reached  room  temperature. 
The  volume  of  the  gas  in  the  burette  is  now  measured  and  a 
caustic  potash  pipette  substituted  for  the  phosphorus  pipette. 
This  requires  somewhat  careful  manipulation  for  the  combustion 
tube  is  still  filled  with  gas  which  must  not  be  allowed  to  diffuse 
into  the  air.  To  accomplish  the  substitution  the  stopcock  of 
the  burette  is  opened  and  the  gas  drawn  out  of  the  capillary 
of  the  phosphorus  pipette  into  the  burette  until  the  liquid  has 
mounted  as  high  as  the  rubber  connecting  tube.  The  glass 
capillaries  of  the  pipette  and  the  combustion  tube  are  separated 
enough  to  allow  a  clamp  to  be  screwed  on  the  rubber  tube  and 
the  phosphorus  pipette  is  disconnected  and  replaced  by  a  caustic 
pipette  whose  liquid  before  making  the  connection  is  blown 
practically  to  the  top  of  the  capillary  by  the  help  of  a  rubber 
tube  attached  to  the  second  bulb.  With  care  this  substitution 
of  one  pipette  for  the  other  may  be  made  with  an  error  of  only  a 
few  tenths  of  a  cubic  centimeter.  The  carbon  dioxide  formed 
from  the  CO  is  then  determined.  Since  it  is  not  feasible  to  drive 
all  the  gas  from  the  combustion  tube  into  the  caustic  the  gas 
should  be  passed  back  and  forth  several  times.  The  method 
of  calculation  of  the  H2  and  CO  follows  from  the  equations: 

H2+CuO  =  H20+Cu 
CO+CuO  =  C02+Cu 


EXPLOSION  AND  COMBUSTION  METHODS  59 

The  metallic  copper  has  practically  the  same  volume  as  the 
copper  oxide.  The  CO2  has  the  same  volume  as  the  CO.  The 
H2  completely  disappears.  Therefore  the  contraction  in  volume 
after  heating  to  250°  is  equal  to  the  H2,  and  the  C02  is  equal  to 
the  CO. 

Methane  is  estimated  by  heating  the  combustion  tube  to 
redness  and  slowly  passing  the  gas  back  and  forth  into  the 
caustic  pipette.  Methane  burns  somewhat  slowly  and  it  is 
wise  to  pass  it  back  and  forth  at  least  four  times.  The  decrease 
in  volume  is  read  after  the  combustion  tube  has  been  cooled 
as  before.  The  equation  for  the  reaction  is: 

CH4+4CuO  =  4Cu+C02+2H20. 

If  the  gas  had  been  passed  back  and  forth  into  a  pipette  filled 
with  water  during  the  combustion  there  would  have  been  no 
change  in  volume  but  since  the  gas  was  passed  into  the  caustic 
pipette  during  the  combustion  process  and  the  C02  was  absorbed 
the  contraction  equals  the  methane. 

It  is  assumed  in  this  calculation  that  CH4  is  the  only  one  of 
the  paraffine  series  present.  This  is  usually  the  case  but  natural 
gas,  Pintsch  gas,  carburetted  water  gas  and  gas  from  coal  dis- 
tilled below  a  red  heat  may  contain  small  proportions  of  ethane 
and  possibly  higher  homologues.  Pentane  vapors  are  present 
in  many  samples  of  natural  gas.  Any  two  constituents  such  as 
methane  and  ethane  may  be  determined  by  this  method  if  during 
the  combustion  at  a  red  heat  the  gases  are  passed  back  and  forth 
into  the  phosphorus  pipette  or  other  pipette  filled  simply  with 
water  and  the  contraction  after  combustion  measured  and  then 
the  COa  determined.  The  calculation  follows  from  the  equations: 

CH4+4CuO  =  4Cu+C02+2H20. 
C2H6+ 7CuO  =  7Cu+2CO2+3H,O. 

In  the  case  of  CH4,  the  volume  is  the  same  after  combustion 
as  before.  In  the  case  of  C2H6  the  volume  has  increased  by  a 
volume  of  CO2  equal  to  the  C2H6.  Any  increase  in  volume  after 
combustion  is  reported  as  C2H6  and  the  volume  of  the  C02  less 
twice  the  C2H«  is  reported  as  CH4. 

In  case  pentane  is  present  the  increase  of  volume  after  com- 


60  GAS  AND  FUEL  ANALYSIS 

bustion  is  four  volumes  for  each  volume  of  pentane  according  to 
the  equation — 

C5H12+16CuO  =  5CO2+6H20. 

It  is  not  usually  feasible  to  distinguish  by  analysis  between 
the  various  higher  hydrocarbons. 

The  copper  oxide  has  been  partially  reduced  to  metallic  copper 
in  the  combustion  and  must  be  re-oxidized  by  drawing  air  through 
the  red  hot  tube.  This  may  be  done  very  conveniently  by  means 
of  an  aspirator  since  no  attention  on  the  part  of  the  analyst  is 
required. 

This  method  is  perhaps  the  most  accurate  of  the  technical 
methods  for  the  estimation  of  CO,  H2  and  CH4  and  is  to  be  com- 
mended because  it  does  not  involve  any  special  equipment 
which  cannot  be  made  by  the  analyst  himself.  It  is  somewhat 
slower  than  the  explosion  methods  but  if  a  quartz  tube  is  available 
it  is  not  a  tedious  process.  A  quartz  tube  is  highly  desirable  since 
glass  tubes  always  break  after  a  time  and  in  breaking  usually 
spoil  the  analysis.  There  is  no  danger  of  oxidation  of  nitrogen 
as  in  the  other  methods  and  a  large  sample  of  gas  may  be  taken 
thus  reducing  the  errors  of  observation  to  a  minimum.  The 
greatest  liability  to  error  comes  from  incomplete  combustion  of 
the  hydrocarbons.  Ethane  is  especially  difficult  to  burn  and 
it  is  desirable  to  repeat  the  combustion  on  the  gas  residue  after 
the  C02  has  been  absorbed  to  make  sure  that  there  is  no  further 
formation  of  C02. 

12.  Detection  of  Minute  Quantities  of  Combustible  Gas.— The 
methods  described  in  the  preceding  paragraphs  have  been  applied 
in  specialized  and  portable  apparatus  for  the  detection  of  small 
amounts  of  combustible  gases,  as  for  instance  in  the  air  of  mines, 
and  also  for  the  removal  of  small  amounts  of  poisonous  gases, 
such  as  carbon  monoxide,  by  gas  masks.  In  one  type  of  detector 
for  mine  gases,  the  methane  is  oxidized  by  a  glowing  spiral  and 
the  heat  of  combustion  is  measured  by  the  resultant  change  in 
the  temperature  or  resistance  of  the  platinum  spiral.  In  another 
type  the  moisture  formed  by  combustion  is  used  as  the  indicator. 
Especially  sensitive  forms  of  copper  oxide  and  other  oxides  were 
developed  during  the  war  by  the  Chemical  Warfare  Service  and 


EXPLOSION  AND  COMBUSTION  METHODS  61 

were  used  in  special  types  of  gas  masks.  The  oxides  were  so 
sensitive  that  they  were  active  and  protected  the  wearer  against 
carbon  monoxide  even  in  winter  weather.  The  same  oxides  have 
been  used  in  portable  apparatus  for  the  detection  of  carbon  mon- 
oxide through  the  heat  developed  by  combustion.  A  still  more 
sensitive  detector  for  carbon  monoxide  in  air  is  found  in  a  mixture 
of  iodic  anhydride  with  fuming  sulphuric  acid  and  pumice.  The 
detection  is  based  on  a  green  color  of  a  transitory  nature  pro- 
duced in  this  mixture  by  minute  quantities  of  carbon  monoxide. 
By  this  means  as  little  as  one  hundredth  of  a  per  cent,  of  carbon 
monoxide  can  be  detected,  and.  by  intensity  of  color  an  approxi- 
mate estimate  of  concentration  up  to  1  per  cent,  can  be  made. 

13.  Oxygen  by  Explosion  or  Combustion. — The  volume  of  oxy- 
gen in  a  gas  may  be  determined  by  explosion  or  combustion 
with  an  excess  of  hydrogen.     The  gas  must  be  free  from  hydrogen 
and  carbon  compounds.     If  an  excess  of  pure  hydrogen  is  added 
and  the  mixture  exploded  or  burned  with  a  platinum  spiral  ac- 
cording to  the  methods  given  in  this  chapter,  the  oxygen  may 
be  calculated  from  the  decrease  in  volume. 

14.  Nitrogen. — There  is  no  desirable  method  for  the  direct 
determination  of  nitrogen,  which  is  always  taken  by  difference. 
This  is  very  unsatisfactory  since,  although  some  of  the  errors  in 
analysis  may  compensate  each  other,  there  is  a  tendency  in  a 
long  analysis  for  them  to  pile  up  on  the  nitrogen. 

The  Jaeger  method  of  combustion  with  copper  oxide  just 
described  allows  all  of  the  gases  other  than  nitrogen  to  be  re- 
moved in  a  single  process  and  affords  a  valuable  check  on  the 
accuracy  of  the  longer  analysis.  A  sample  of  100  c.c.  of  the  gas 
to  be  analyzed  is  passed  through  the  combustion  tube  at  red 
heat  and  into  caustic.  The  CO2,  CO,  H2,  and  CnHm  will  all 
disappear  in  the  process  as  will  also  the  oxygen  if  it  is  present  in 
only  small  amount.  The  residue  will  be  nitrogen  and  possibly 
oxygen  which  may  be  removed  by  phosphorus. 

15.  Form  of  Record  of  Gas  Analysis. — There  may  of  course 
be  great  variation  in  methods  of  keeping  records  of  gas  analyses. 
The  record  should  in  every  case  however  be  full  enough  to  show 
every  step  of  the  operation.     The  following  record  is  given  as  a 
sample. 


62  GAS  AND  FUEL  ANALYSIS 

ANALYSIS  OF  ILLUMINATING  GAS 

at  Chemical  Laboratory,  University  of  Michigan,  Sept.  9,  1917 

Sample  99.4-0.3  =  99.1  c.c. 

After  KOH  97.4  CO2          =2.0  c.c.  =2.0% 

After  Br2  92 . 6  C2H4,  etc.,  4 . 8  c.c.      4 . 8 

After  P  92.2  O2  0.4  c.c.      0.4 

After  Cu2Cl2  84.8-0.3=84.5  CO  7. 4  c.c.      7.5 

First  explosion: 

Sample  9.4-0.3=  9.1 

Air  to  97.9-0.3  =  97.6 

After  explosion  83.0                                       Contraction  =14.9 

After  KOH  79.2                                                   CO2  =  3.8 

After  P  71.0                                       Excess  O2       =8.2 

Calculations: 

Factor  to  give  percentage  Q  1X99T  =  9 ' 37 

CH4=3.8X9.37  =35.6% 

H2  =2/3(14. 9-2X3. 8)9. 37  =45.6% 

N2  =  [9.1-(3. 8+4. 87)]9.37  =  4.0% 
Exploding  gases: 

3.8c.c.  CH4+    .6c.c.  O2  =11. 4  c.c. 

4.9c.c.     H2+2.4c.c.O2  =   7.3  c.c. 


18.7 

Non-exploding  gases: 

97.6-18.7  78.9 

_,     .    non-exploding     78.9 
Ratl°      exploding      =18-7  =  4-2 

Second  explosion: 

Sample  9.2-0.3=  8. 9  c.c. 

Air  to  95.0-0.3  =  94.7 

After  explosion  80 . 4                      Contraction  14 . 6 

After  KOH  76.7                      CO,                 3.7 

After  P  70.0                      Excess  O2       6.7 

Calculations : 

Factor  to  give  percentage  g  Qx99  1  =9 ' 58 

CH4  =3.7X9.58  =35.4% 

H2  =  2/3(14.6-2X3.7)9.58)     =46.0 
N2  =[8.9-(3.7+4.8)]9.58         =  3.8 


EXPLOSION  AND  COMBUSTION  METHODS  63 

Exploding  gases: 

3.7c.c.  CH4+7.4c.c.  O2  =  ll.lc.c. 
4.8c.c.     H2+2.4c.c.  O2=  7.2 


18.3 

Non-exploding  gases: 
94.7-18.3  =76.4 

.    non-exploding       76 . 4 
Ratio  —    — r— p —  -  =  <0  0  =4.2 
exploding          18.3 

Summary  of  analysis: 

I  II                          Average 

CO2                               2.0  2.0% 

C2H4,  etc.,                   4.8  4.8 

O2                                  0.4  0.4 

CO                               7.5  7.5 

CH4                             35.6  35.4                         35.5 

H2                                45.6  46.0                        45.8 

N»                                  4.0  3.8                          3.9 


99.9% 


CHAPTER  V 

VARIOUS  TYPES  OF  APPARATUS  FOR  TECHNICAL  GAS 

ANALYSIS 

1.  Introduction. — Chapter  II  describes  the  apparatus  which 
the  author  believes  best  adapted  to  technical  gas  analysis  and 
gives  detailed  directions  for  its  manipulation.     The  present  chap- 
ter will  describe  various  other  forms  of  technical  apparatus 
especially  those  which  first  embodied  valuable  principles.     The 
number  of  modifications  is  legion  and  no  attempt  will  be  made  to 
even  enumerate  them.     The  order  of  description  will  in  general  be 
historical. 

2.  Schlosing  and  Rolland's  Apparatus. — Perhaps  the  earliest 


FIG.  14. — Schlosing  and  Holland's  apparatus. 

successful  attempt  to  devise  an  apparatus  for  the  rapid  analysis 
of  industrial  gas  was  that  of  Schlosing  and  Holland1  who  de- 
vised a  simple  apparatus  which  foreshadowed  closely  the  modern 
type.  Their  apparatus  apparently  attracted  little  attention 
1  Annales  de.  Chim.,  Series  4,  t.14,  55  (1868). 

64 


APPARATUS  FOR  TECHNICAL  GAS  ANALYSIS  65 

partly  because  its  description  was  embodied  in  a  long  article  on 
the  ammonia-soda  process  whose  title  did  not  contain  any  ref- 
erence to  gas  analysis.  The  original  cut  of  their  apparatus  is 
reproduced  as  Fig.  14  as  it  still  may  serve  as  a  model  for  a  chemist 
who  has  to  improvise  his  own  apparatus.  The  following  descrip- 
tion of  the  apparatus  is  taken  from  the  original  work.  In  the 
upper  left  hand  corner  of  the  cut  are  seen  four  lead  pipes  of  small 
diameter  coming  from  various  pieces  of  apparatus  in  the  plant.  A 
rubber  tube  d  connects  any  one  of  these  with  the  copper  tube  t 
to  which  is  attached  an  aspirator.  The  burette  a  terminates  at 
the  top  in  a  tee  of  almost  capillary  tubing,  one  arm  of  which  con- 
nects to  the  gas  supply  through  the  cock  r  and  the  other  to  the 
pipette  b.  No  mention  is  made  of  a  clamp  on  the  rubber  tube 
between  a  and  b  but  necessarily  such  must  have  been  used.  To 
draw  a  sample  of  gas  the  cock  r  is  opened  and  the  levelling  bottle 
c  is  raised  until  the  water  fills  the  burette  and  reaches  r.  The 
gas  formerly  in  the  burette  is  now  in  the  pipe  t  out  of  which  it  is 
swept  by  the  stream  of  gas  which  is  constantly  flowing.  The 
bottle  is  then  lowered  until  the  gas  has  passed  below  the  100  mark. 
The  aspirator  is  stopped,  the  rubber  tube  d  disconnected  and  the 
bottle  raised,  r  being  again  opened  until  the  level  of  the  water  in 
the  burette  is  at  100  and  is  at  the  same  time  coincident  with  the 
level  of  the  water  in  the  levelling  bottle.  The  burette  will  then 
contain  100  volumes  of  gas  at  atmospheric  pressure.  The  gas 
is  then  passed  back  and  forth  into  the  absorption  pipette  b  filled 
with  caustic  potash  and  containing  glass  tubes  to  increase  the 
absorptive  surface.  The  volume  in  the  burette  is  then  read  as 
before  and  the  decrease  in  volume  reported  as  C02. 

3.  Orsaf  s  Apparatus. — The  original  form  of  the  Orsat1  appa- 
ratus is  practically  the  same  as  that  frequently  used  today,  as 
will  be  seen  by  Fig.  15  which  is  a  reproduction  of  the  original  cut. 
It  consists  of  a  water-jacketed  gas  burette  terminated  at  its  upper 
end  by  a  branched  glass  capillary  tube.  The  pipettes,  in  order 
from  right  to  left,  contain  caustic  potash,  alkaline  pyrogallate  and 
cuprous  chloride.  The  cock  I  on  the  branched  capillary  serves 
for  the  connection  of  a  platinum  capillary  in  which  hydrocarbons 
mixed  with  air,  and  added  hydrogen  if  necessary,  may  be  burned. 
The  sample  of  gas  is  brought  to  the  burette  by  the  water-aspira- 

1  Annales  des  Mines,  Series  7,  t.8,  485  (1875). 
5 


66 


GAS  AND  FUEL  ANALYSIS 


tor  KLM  which  sucks  a  rapid  stream  of  gas  through  the  cock  R 
and  the  dust  filter  P.  The  operation  of  the  apparatus  will  be 
evident  to  anyone  who  has  read  the  three  preceding  chapters. 

Many  modifications  of  this  burette  have  been  proposed  since 
it  was  first  described,  but  the  principle  has  not  been  altered.  One 
group  of  workers  has  increased  the  complexity  of  the  apparatus  in 
an  attempt  to  increase  speed  of  manipulation.  The  most  note- 
worthy change  of  this  sort  is  probably  the  introduction  of  the 


FIG.  15. — Orsat  apparatus.     Original  form. 


bubbling  pipette  in  which,  by  a  three-way  cock  on  the  top  of  each 
pipette,  the  gas  is  made  to  pass  down  a  central  tube  and  bubble  up 
through  the  liquid  of  the  pipette  to  be  later  drawn  from  the  top  of 
the  pipette  when  the  three-way  cock  is  thrown  to  its  second  posi- 
tion. There  are  decided  objections  to  complication  in  any  form 
of  apparatus  which  may  receive  rough  treatment  in  transportation 
and  which  is  frequently  handled  carelessly  by  its  operators. 

The  usual  modifications  of  the  Orsat  apparatus  possess  at  least 
four  glass  stopcocks  on  the  various  outlets  of  the  branched  tee. 


APPARATUS  FOR  TECHNICAL  GAS  ANALYSIS 


67 


Unless  the  apparatus  is  always  manipulated  by  a  skilled  operator 
it  is  almost  inevitable  that  some  of  the  alkaline  reagent  from  the 
pipettes  will  be  drawn  into  these  stopcocks.  It  is  apparently 
equally  inevitable  that  the  cocks  will  as  a  consequence  stick  and 
become  broken.  The  branched  tee  is  itself  a  source  of  trouble 
since  it  is  fragile  and  difficult  to  clean  when  stopped.  In  Fig. 
16  is  shown  a  modification  of  the  Orsat  apparatus  due  to  Allen  and 

Moyer  which  commends  itself 
for  its  simplicity  and  durability. 
The  capillary  glass  tube  is  re- 
placed by  one  of  hard  rubber  and 
the  glass  stopcocks  are  replaced 
by  pinchcocks  which  are  practi- 
cally as  satisfactory.  The  pip- 
ettes themselves  are  of  the  test 
tube  type  and  are  closed  at  the 
top  with  a  soft  rubber  stopper 
which  is  pressed  against  the 
upper  shelf  by  the  screw  which 
supports  the  cup  in  which  each 
pipette  rests.  This  gives  a  firm 
and- yet  elastic  support  for  the 
pipettes  which  prevents  breakage 
in  shipment. 

The  method  of  operating  all 
Orsat  burettes  is  the  same.     The  / 

water  of  the  burette  should  be  saturated  with  gas  similar  to  that  ' 
which  is  to  be  analyzed.  The  gas  is  taken  into  the  burette 
through  the  end  of  the  capillary  projecting  out  of  the  left  hand 
side  of  the  case.  If  the  sample  is  drawn  directly  from  the  smoke 
flue  the  precautions  given  in  Chapter  I  on  Sampling  must  be 
observed.  In  any  case  the  burette  is  filled  with  gas  which  is 
then  wasted  through  the  fourth  side  arm  into  the  outside  air, 
thus  getting  rid  of  the  air  which  was  in  the  capillary  tube  of  the 
instrument.  The  sample  of  gas  is  now  drawn  into  the  burette 
and  measured  with  the  precautions  given  in  Chapter  I. 
addition  to  the  gas  which  is  in  the  burette  there  is  a  volume 
about-J.  c.c.  in  the  capillary  tube  which  is  entirely  neglected. 
The  gas  is  passed  into  the  caustic  pipette  and  CO2  determined 


FIG.  16. — Orsat  apparatus.     Allen- 
Moyer  modification.  * 


tie 

In, 
of  I 

ed.  1 


68  GAS  AND  FUEL  ANALYSIS 

as  described  in  §  1  of  Chapter  III,  then  into  the  second  pipette 
filled  with  pyrogallate  for  oxygen  (§  4  of  Chapter  III),  then 
into  the  third  pipette  filled  with  cuprous  chloride  for  CO  (§  6  of 
Chapter  III). 

This  apparatus  is  much  used  for  analysis  of  smoke  gases  and 
it  is  sufficiently  accurate  for  this  purpose.  The  errors  which 
arise  from  the  failure  of  the  gas  in  the  capillary  to  come  into 
contact  with  the  reagent  will  hardly  be  more  than  0.1  c.c.  for 
each  of  the  gases.  The  tendency  will  be  for  the  oxygen  to  be 
slightly  high  due  to  some  CC>2  which  did  not  get  into  the  caustic 
pipette  and  for  the  CO  to  be  high  due  to  oxygen  which  did  not 
get  into  the  pyrogallate  pipette. 

The  Orsat  apparatus  is  not  usually  employed  for  gases  like 
1  illuminating  gas  where  many  constituents  have  to  be  deter- 
mined, although  other  absorption  pipettes  and  even  explosion 
pipettes  have  sometimes  been  made  a  part  of  the  instrument. 
The  errors  mentioned  above  due  to  the  gas  remaining  in  the 
capillary  increase  with  the  length  of  the  capillary  and  it  becomes 
preferable  to  use  the  burette  with  detachable  pipettes. 

4.  Bunte's  Burette. — Dr.  H.  Bunte1  in  1877  described  his 
burette  which  although  in  the  main  obsolete  still  has  some  uses 
and  is  illustrated  in  Fig.  17.  It  consists  of  a  burette  closed  at 
the  top  by  a  three  way  cock  a  carrying  a  funnel  tube,  and  at  the 
bottom  by  a  cock  b.  The  zero  of  the  burette  is  somewhat  above 
the  lower  cock. 

A  levelling  bottle  such  as  is  used  with  the  ordinary  Hempel 
type  of  gas  burette  is  to  be  connected  to  the  lower  cock.  The 
sample  of  gas  is  drawn  into  the  burette  as  usual  and  its  volume 
may  be  read  as  usual.  The  method  of  reading  the  volume 
prescribed  by  Bunte  is  unusual.  A  sample  of  gas  slightly  larger 
than  100  c.c.  is  to  be  taken  into  the  burette  and  the  volume  com- 
pressed until  it  reads  exactly  100.  Water  is  now  poured  into 
the  funnel  tube  to  the  mark  m  etched  upon  it  and  cock  a  is  opened 
to  communicate  with  the  funnel  tube  which  is  unstoppered. 
Some  gas  bubbles  through  the  cock  and  the  liquid  above  it  and 
escapes  into  the  air.  The  bore  of  the  cock  is  so  small  that  no 
water  flows  down  and  after  the  bubbling  has  ceased  the  volume 
of  gas  in  the  burette  is  still  100  c.c.  measured  under  the  pressure 

1  Jour,  fur  GasbeL,  1877,  447. 


APPARATUS  FOR  TECHNICAL  GAS  ANALYSIS 


69 


of  the  atmosphere  plus  the  column  of  water  in  the  funnel  tube. 
The  volume  of  the  gas  is  always  to  be  read  under  these  condi- 
tions. In  order  to  introduce  an  absorbent  such  as  NaOH  into 
the  burette  a  partial  vacuum  is  produced  by  opening  the  lower 
cock  and  lowering  the  levelling  bottle.  The  cock  6  is  then 
closed,  the  levelling  bottle  disconnected  and  the  reagent  in  a 
small  dish  is  placed  below  the  cock  6  so  that  the  tip  of  the  cock 
is  immersed.  On  opening  the  cock  some  of  the  rea- 
gent will  be  sucked  into  the  burette.  The  burette  is 
then  shaken  to  facilitate  absorption,  care  being  taken 
to  hold  it  only  by  the  tips  so  that  the  heat  of  the 
hands  will  not  change  the  temperature  of  the  gas.  To 
read  the  volume  after  absorption  the  funnel  tube  on 
the  top  of  the  burette  is  again  filled  with  water,  and 
the  upper  cock  opened.  Water  flows  into  the  burette 
and  more  water  is  added  to  the  funnel  until  with  the 
upper  cock  still  open  the  water  remains  stationary 
on  the  mark  m.  Conditions  are  now  as  they  were  at 
the  first  reading  and  the  volume  is  again  read.  The 
diminution  in  volume  if  NaOH  was  the  reagent,  is  as 
usual  reported  as  CO2. 

Oxygen  is  determined  by  alkaline  pyrogallate  (§4 
of  Chapter  III).  To  avoid  diluting  the  reagent  the 
dilute  caustic  in  the  burette  is  sucked  out  as  far  as 
possible  and  20  c.c.  of  the  pyrogallate  introduced. 
The  burette  is  shaken  at  intervals  for  five  minutes 
and  then  rinsed  with  fresh  water  introduced  through  the  funnel 
tube,  the  pyrogallate  being  allowed  to  flow  out  of  the  lower 
stopcock.  As  soon  as  the  walls  of  the  burette  are  rinsed  clean 
the  bottom  stopcock  is  closed  and  the  volume  read  as  before 
with  the  top  stopcock  open  and  the  funnel  tube  filled  with  water. 
Carbon  monoxide  is  absorbed  by  acid  cuprous  chloride  as 
usual  (§  6  of  Chapter  III),  but  a  very  considerable  amount  of 
preliminary  manipulation  is  necessary.  The  alkaline  pyrogallate 
must  be  thoroughly  washed  out  by  water  flowing  through  the 
burette  and  then  replaced  by  HC1  sp.  gr.  1.12.  When  this  has 
been  done  the  Cu2Cl2  reagent  may  be  added  and  after  the 
absorption  the  volume  measured  with  the  funnel  tube  filled  with 
dilute  HC1. 


FIG.  17.— 
Bunte  gas 
burette. 


70 


GAS  AND  FUEL  ANALYSIS 


The  only  advantage  which  a  burette  of  this  type  can  claim  is 
its  portability.  Its  manipulation  is  cumbrous,  the  introduction 
of  the  large  volumes  of  wash  water  changes  the  composition  of 
the  gas,  and  the  temperature  of  the  burette,  which  is  usually 
not  jacketed,  is  almost  certain  to  change  unless  very  unusual 
precautions  are  observed  to  keep  it  from  contact  with  the 
hands  of  the  operator  and  to  have  the  temperature  of  the  reagent 
and  wash  water  the  same  as  that  of  the  room  where  the  operation 
is  being  carried  on.  The  Orsat  apparatus  is  preferable  for  almost 
all  purposes. 

6.  Chollar   Tubes.— Mr.    B.    E.    Chollar1   in    1888   modified 

A. 


1 

t 

L 

; 
: 
|: 

r 

=f 
v\ 

\i 

7 

F 

FIG.  18. — Chollar  tubes  for  gas  analysis. 

Cooper's  eudiometer  and  produced  a  very  practical  and  simple 
combination  burette  and  pipette.  In  Fig.  18  at  A  are  seen  three 
of  the  Chollar  tubes  in  a  rack.  The  zero  point  is  the  top  of  the 
bulb  and  the  graduations  start  at  the  bottom  of  the  bulb  and  ex- 
tend down  to  the  bend  in  the  tube.  The  bulbed  portion  may 
1  Proc.  Western  Gas  Association,  1893,  219. 


APPARATUS  FOR  TECHNICAL  GAS  ANALYSIS  71 

occupy  varying  proportions  of  the  total  volume  and  since  it  is 
not  graduated  a  tube  must  be  chosen  proportioned  properly 
for  the  analysis  to  be  made.  Of  the  three  burettes  shown  at  A, 
that  on  the  right  is  called  a  10  per  cent,  burette  because  the 
graduations  cover  only  10  per  cent,  of  the  total  volume.  The 
middle  burette  is  a  25  per  cent,  burette,  and  the  burette  on  the 
left  is  a  50  per  cent,  burette,  provided  also  with  an  upper  stop- 
cock which  is  convenient,  but  not  necessary  for  all  the  forms. 

It  is  assumed  that  a  plentiful  supply  of  gas  for  analysis  is  avail- 
able and  that  it  is  under  pressure.  A  rubber  tube  is  slipped  into  the 
burette  round  the  bend  and  up  to  the  top  through  which  gas  is 
blown  until  the  air  is  displaced.  It  is  safer  to  fill  the  tube  with 
water  and  displace  this  with  the  gas.  The  rubber  tube  slips 
into  the  burette  more  readily  if  it  is  wet.  When  the  burette  is 
completely  filled  with  gas  it  is  immersed  in  the  cylinder  of  water 
B  far  enough  to  seal  the  outlet  and  the  rubber  tube  is  withdrawn. 
The  burette  is  now  pressed  completely  under  the  water  and  kept 
there  by  the  weighted  cover  C  for  a  few  minutes  until  the  gas 
has  attained  the  temperature  of  the  water  which  should  be  at 
room  temperature.  The  top  of  the  burette  is  then  grasped  by 
the  tip  of  the  fingers  to  avoid  warming  the  gas  and  the  burette 
is  raised  until  the  meniscus  inside  of  the  burette  coincides  with 
the  surface  of  the  water  in  the  glass  cylinder  when  the  gas  vol- 
ume is  read  at  atmospheric  pressure.  In  case  the  volume  of  the 
gas  has  increased  through  expansion  so  that  the  meniscus  is 
below  the  graduations  a  portion  of  the  gas  must  be  removed  by 
closing  the  lower  end  of  the  burette  with  the  thumb  while  it  is 
still  under  water  and  then  by  raising  and  tilting  the  burette 
causing  a  few  bubbles  to  pass  into  the  short  arm  from  which  they 
escape  into  the  air  when  the  thumb  is  removed, 

To  introduce  reagents,  a  portion  of  the  water  is  sucked  from 
the  short  arm  of  the  burette  by  a  pipette  as  shown  at  D.  Suf- 
ficient water  must  of  course  be  left  to  seal  the  burette.  Suf- 
ficient reagent  such  as  caustic  sodajs  then  introduced  to  com- 
pletely fill  the  short  arm  which  is  tightly  closed  by  a  rubber 
stopper  or  the  thumb.  The  burette  is  then  inverted  and  shaken 
until  absorption  is  believed  to  be  complete.  The  gas  which  may 
have  gotten  into  the  short  arm  is  now  worked  back  into  the  body 
of  the  burette  by  turning  the  burette  almost  horizontal  and  the 


72  GAS  AND  FUEL  ANALYSIS 

burette  is  again  immersed  in  the  large  cylinder.  The  rubber 
stopper  is  removed  after  the  outlet  is  sealed  with  water,  water 
enters  to  replace  the  gas  absorbed  and  the  volume  of  the  gas  is 
read  as  at  first. 

The  usual  reagents  for  carbon  dioxide,  unsaturated  hydro- 
carbons, oxygen  and  carbon  monoxide  may  be  used.  A  solution 
of  arsenious  oxide  is  recommended  for  hydrogen  sulphide. 

To  wash  out  one  reagent  before  adding  another  the  burette 
is  placed  on  the  stand  shown  at  E  in  Fig.  18  with  its  open  arm 
pointing  down  in  a  beaker  of  water.  The  reagent  being  heavier 
than  water  tends  to  flow  out.  The  washing  may  be  accelerated 
by  passing  water  into  the  burette  through  a  rubber  tube.  The 
instrument  is  very  readily  portable  and  after  a  little  experience 
results  of  considerable  accuracy  may  be  rapidly  obtained. 

6.  Instruments  for  Recording  Carbon  Dioxide  in  Flue  Gases. — 
There  are  a  number  of  commercial  instruments  on  the  market 
which  aim  to  make  a  continuous  record  of  the  percentage  of 
carbon  dioxide  in  stack  gases.  These  instruments  usually  derive 
their  motive  power  from  an  aspirator  which  sucks  a  sample  of 
flue  gas  through  a  dust  filter  and  then  through  the  analyzing 
mechanism.  Most  of  these  mechanisms  imitate  the  action  of  the 
analyst  when  he  sucks  in  a  buretteful  of  gas,  passes  it  into  caustic 
solution  and  then  measures  the  decrease  in  volume.  In  the 
machine  the  filtered  gas  is  made  to  exactly  fill  one  measuring 
chamber,  then  passed  into  caustic  and  then  into  a  second 
chamber  where  its  volume  is  measured  by  the  height  to  which  it 
raises  a  small  gas  holder  or  by  some  other  mechanical  means. 
A  pen  attached  to  the  gas  holder  indicates  on  a  chart  the  height 
of  the  gas  holder  and,  if  the  chart  and  instrument  are  correctly 
adjusted,  it  records  directly  the  percentage  of  carbon  dioxide. 
Machines  of  the  above  type  give  intermittent  readings.  The 
Uehling  carbon  dioxide  machine  operates  continuously  and  with- 
out measuring  chambers.  It  measures  the  percentage  of  carbon 
dioxide  by  recording  the  difference  in  suction  caused  by  the  dimi- 
nution in  volume  of  the  gas  after  removal  of  the  carbon  dioxide 
by  caustic.  Two  standard  diaphragms  are  inserted  in  the  line 
through  which  the  gas  flows  and  the  dry  caustic  absorption  cylinder 
and  the  recording  manometer  are  placed  between  them.  With  air 
flowing  through  the  apparatus  a  certain  suction  will  be  registered. 


APPARATUS  FOR  TECHNICAL  GAS  ANALYSIS          73 

With  gases  containing  carbon  dioxide  a  higher  suction  will  be 
registered  because  of  the  smaller  volume  of  gas  passing  the  second 
diaphragm.  A  detailed  description  of  several  of  these  instru- 
ments together  with  results  of  tests  on  them  has  been  made  by 
the  Bureau  of  Mines.1  Some  of  them  work  very  well  but  it  must 
be  remembered  that  none  of  them  are  fool  proof  and  that  ail  of 
them  require  rather  frequent  and  expert  adjustment. 

7.  Methods  of  Gas  Analysis  Depending  upon  Thermal  Con- 
ductivity.— This  method  depends  on  the  difference  in  thermal 
conductivity  of  different  gases.     A  carefully  calibrated  platinum 
wire  is  heated  with  a  constant  electric  current.     The  gas  to  be 
tested  is  then  made  to  flow  through  the  tube  containing  the  wire 
and  the  difference  of  the  resistance  of  the  hot  wire  is  measured. 
If  the  gases  have  not  reacted  with  each  other  or  been  subjected 
to  chemical  change  under  the  influence  of  the  hot  wire,  this  meas- 
urement allows  the  calculation  of  the  heat  conductivity  of  the 
gas,  and  in  case  only  two  constituents  are  present  it  permits  the 
proportions  of  each  to  be  calculated.     By  the  use  of  a  series  of 
conductivity  tubes  with  proper  absorbents  or  oxidizing  appa- 
ratus between  them  a  continuous  test  may  be  made  of  the  com- 
position of  gases  with  a  number  of  different  constituents.     The 
apparatus  may  be  made  recording.     It  is  largely  one  of  the  devel- 
opments of  the  Bureau  of  Standards  for  war  needs2  and  is  hardly 
yet  a  technical  instrument  for  general  purposes. 

8.  Gas  Analysis  by  Optical  Methods. — The  refraction  of  a 
beam  of  light  passing  through  a  gas  is  in  general  proportional  to 
the  density  of  the  gas.     While  the  differences  in  the  index  of 
refraction  are  small  they  may,  with  rather  complicated  appa- 
ratus, be  accurately  measured.     The  method  is  most  readily  ap- 
plicable where  there  are  only  two  constituents  in  a  gas  mixture. 
An  instrument  called  the  interferometer  or  refractometer  has 
been  devised  for  this  work  but  it  is  to  be  regarded  more  as  a 
scientific  instrument  than  one  for  technical  use,  although  Burrell 
and  Seibert3  state  that  the  instrument  may  be  successfully  used 
for  technical  analysis  of  the  following:  mine  air  for  carbon  dioxide 
and  methane;  manufactured  hydrogen,  chlorine  and  other  gases 
for  purity;  illuminating  gas  for  benzol,  and  flue  gases  for  carbon 
dioxide.     Edwards4  has  published  a  critical  review  of  the  appli- 
cation of  the  interferometer  to  gas  analysis. 

1  J.  F.  Barkley  and    S.  B.  Flagg.     Instruments  for  Recording  Carbon 
Dioxide  in  Flue  Gases.     Bulletin  91.     Bureau  of  Mines,  1916. 

2  Weaver  and  others,  Jour.  Ind.  and  Eng.  Chem.  1920. 


T> _J 


CHAPTER  VI 

EXACT  GAS  ANALYSIS 

1.  Historical. — Lavoisier  in  his  Traite*  Elementaire  de  Chemie 
published  in  1789  devoted  Chapter  II  of  Book  III  to  Gasometry 
or  "The  Measurement  of  Weight  and  Volume  of  Gaseous  Sub- 
stances." He  described  eudiometers,  a  gasometer  of  the  bell 
jar  type,  and  methods  of  separation  of  certain  gases  by  absorp- 
tion and  explosion  as  well  as  the  mathematical  method  of  making 
correction  for  temperature  and  pressure. 

Bunsen  and  Playfair1  in  a  paper  "On  the  Gases  Evolved  from 
Iron  Furnaces"  presented  in  1845  what  was  perhaps  the  first 
serious  attempt  to  develop  methods  of  gas  analysis  for  technical 
investigation.  The  methods  published  in  this  paper  formed  the 
basis  of  Bunsen's  classic  book  "  Gasometrische  Methoden" 
published  in  1857.  Bunsen  used  a  graduated  cylindrical  eudi- 
ometer inverted  over  a  trough  of  mercury  both  for  measuring 
the  volume  of  the  gas  and  for  carrying  out  analysis  by  absorp- 
tion and  explosion.  It  was  necessary  to  determine  the  tempera- 
ture and  pressure  of  the  gas  when  each  reading  of  volume  was 
made  and  to  make  arithmetical  corrections  to  bring  the  volume 
to  standard  conditions.  It  was  possible  to  work  accurately 
with  his  apparatus  but  it  has  been  replaced  by  simpler  forms 
which  allow  more  rapid  work. 

Regnault  and  Reiset2  in  a  paper  on  the.  respiration  of  animals 
developed  a  eudiometer  which  was  capable  of  accurate  work 
but  was  very  cumbrous. 

Doyere  in  J8483  exhibited  before  the  French  Academy  of 
Sciences  apparatus  for  gas  exact  analysis  and  two  years  later4 
presented  details  of  the  remarkably  complete  and  ingenious 
apparatus  which  he  had  devised.  He  used  a  separate  pipette 

1  British  Ass.  for  Advancement  of  Science,  1845,  142. 

2  Ann.  de  Chim.  et  de  Phys.  (3),  26,  299  (1849). 

3  Comptes  rendus  de  I' Academic  de  Science,  Feb.,  1848. 

4  Annales  de  Chimie,  3  Series,  28,  5,  (1850). 

74 


EXACT  GAS  ANALYSIS  75 

for  each  reagent,  measured  his  gases  saturated  with  moisture 
instead  of  dry,  and  by  means  of  a  mechanical  compensator 
avoided  all  corrections  for  change  in  gas  volume  due  to  tempera- 
ture and  pressure.  He  absorbed  carbon  dioxide  by  caustic 
potash  and  estimated  oxygen  by  explosion  or  by  absorption  with 
ammoniacal  cuprous  chloride,  two  pipettes  being  used  in  series 
followed  by  a  third  containing  dilute  sulphuric  acid.  He  also 
studied  the  estimation  of  hydrogen  by  explosion. 

W.  Hempel  in  the  second  edition  of  his  Gas  Analysis  (1889) 
described  a  modification  of  Doyere's  method  in  which  he  measured 
the  gas  volume  in  a  bulb,  varying  the  pressure  of  the  gas  at  each 
reading  so  that  its  volume  always  filled  the  bulb  to  a  definite 
mark.  The  pressure  under  which  the  gas  stood  was  then  meas- 
ured and  correction  mathematically  made  to  find  the  volume 
under  standard  conditions. 

2.  General    Methods. — These    earlier    processes    with    their 
complications  were  necessitated  by  the  imperfections  of  apparatus, 
especially  stopcocks  which  could  not  be  relied  on  to  be  gas- 
tight.     With  the  development  of  reliable  stopcocks  came  the 
development  of  apparatus  so  that  now  there  is  little  need  to  use 
any  of  these  older  processes.     The  methods  of  exact  gas  analysis 
are  now  in  general  the  same  as  those  employed  in  technical 
analysis  but  with  greater  attention  paid  to  the  elimination  of 
minor  errors.     The  gas  burette  is  graduated  more  accurately 
and  an  attempt  is  made  to  read  to  hundredths  of  a  cubic  centi- 
meter instead  of  tenths.     Correction  is  made  either  arithmetically 
or  mechanically  for  variations  in  temperature  and  pressure  of 
the  gas  during  analysis.     Mercury  is  used  instead  of  water  as 
the  confining  liquid  in  the  burette  and  errors  due  to  diffusion 
in  the  pipette  are  prevented.     Special  methods  are  sometimes 
introduced  for  the  estimation  of  minute  constituents  of  the 
gas. 

3.  Corrections   for  Temperature   and   Pressure. — According 
to  the  law  of  Boyle  the  volume  of  any  gas  varies  inversely  as  the 
pressure  and  according  to  the  law  of  Gay  Lussac  all  gases  expand 
under  constant  pressure  by  the  same  amount — about  1/273  of 
their  volume — when  heated  from  0°  C.  to  1°  C.,  and  the  same  for 
each  succeeding  degree.     The  volume  of  a  gas  is  almost  univer- 
sally expressed  in  scientific  work  as  that  which  it  would  occupy 


76  GAS  AND  FUEL  ANALYSIS 

if  completely  dry  and  at  a  temperature  of  0°  C.,  and  a  pressure 
of  760  mm.  of  mercury.  For  technical  purposes  the  gas  is  fre- 
quently calculated  to  the  volume  which  it  would  have  at  60°  F. 
and  30  in.  of  mercury  pressure  when  saturated  with  water.  The 
formulae  for  this  calculation  are  given  in  §  4  of  Chapter  VII  on 
the  Heating  Value  of  Gas. 

The  formula  for  the  reduction  of  the  volume  of  a  dry  gas  to 
0°  and  760  mm.  dry  follows  from  the  laws  stated. 

v  __  V  __  p^  Vp 

"  M7     °r  V°-(l-.00367t)760 
~7 


If  the  gas  as  measured  was  saturated  with  moisture  at  say 
60°  F.  and  it  should  actually  be  chilled  to  0°  C.  most  but  not  all 
of  the  water  would  be  condensed.  It  is  usual  in  calculations 
to  assume  either  that  the  gas  becomes  completely  dried  which 
is  the  usual  assumption  or  that  the  water  all  remains  in  the 
vapor  state  which  is  less  frequently  assumed.  The  formula 
given  above  will  be  the  one  used  in  the  latter  case  where  the 
water  vapor  is  assumed  to  obey  the  gas  laws  without  condensing, 
just  as  nitrogen  or  hydrogen  would. 

If  the  gas  is  to  be  reduced  to  standard  conditions,  dry,  the 
volume  of  the  water  vapor  must  be  deducted.  Since  the 
assumption  is  that  the  gas  is  saturated  with  moisture  at  the 
temperature  "t"  the  proportion  of  moisture  will  be  a  constant 
which  may  be  expressed  either  in  terms  of  volume  or  more 
conveniently  in  terms  of  barometric  pressure.  Table  I  in  the 
Appendix  gives  the  vapor  pressure  of  water,  "a,"  for  each  1°  C. 
within  the  limits  usually  required.  The  formula  for  reduction 
of  the  volume  of  a  gas  read  when  saturated  with  moisture,  to 
its  volume  when  dry  at  0°  C.  and  760  mm.  is  therefore  as  follows: 


(1  -.003671)760 

If  the  readings  are  in  the  Fahrenheit  scale  and  in  inches  of 
barometric  pressure  the  formula  becomes 

V(p-a) 


EXACT  GAS  ANALYSIS 


77 


A. 


Rubb 
Con, 


Calibt  ati'on 
MaH 


ection 


4.  Description  of  Gas  Burettes.^ — The  burette  for  technical 
analysis  does  not  allow  an  accuracy  greater  than  0.1  c.c.  and  the 
probable  error  is  more  nearly  0.2  c.c.  The  errors  are  in  part 
due  to  the  coarse  graduations  of  the  cylindrical  burette  tube 
and  in  part  to  liability  to  change  in  the  temperature  and  pressure 
under  which  the  gas  volume  is  read.  A  device  for  automatically 
correcting  for  change  in  tempera- 
ture and  barometric  pressure  was 
devised  by  Petterson1  in  an  ap- 
paratus for  the  analysis  of  air. 
This  was  quickly  adapted  by 
Hempel  to  his  gas  burette  and 
as  used  by  him  consisted  of  a 
closed  tube  connected  to  one  arm 
of  a  manometer  whose  other  end 
connected  with  one  tip  of  a  three- 
way  cock  at  the  top  of  the  bur- 
ette. The  volume  of  the  gas 
instead  of  being  read  at  a  change- 
able atmospheric  pressure  was  to 
be  read  at  the  unchanging  pres- 
sure in  the  closed  compensating 
tube.  The  modification  of  this 
type  of  apparatus  developed  by 
the  author2  is  shown  in  Fig.  19. 

The  burette  has  a  specially 
bored  stopcock  as  shown  in  the 
sketch  which  allows  communica- 
tion to  be  established  through  the 
stopcock  between  the  burette  and 
the  compensating  tube.  The 

latter  consists  of  a  U  tube  manometer  shown  in  A  of  Fig.  19 
connected  to  the  burette  by  a  single  rubber  connection  at  a, 
placed  so  that  gas  never  comes  in  contact  with  the  rubber  and 
there  can  be  no  possibility  of  leakage — a  fault  of  the  Hempel  type 
of  apparatus.  The  other  end  of  the  U  tube  bends  down  and 
terminates  in  a  tube  about  the  same  diameter  as  the  burette  and 

lZeit.  anal  Chem.,  25,467  (1886). 

2 Jour.  Am.  Chem.  Soc.,  22,  343  (1900). 


' 


c. 


TT 


FIG.  19. — Details  of  gas  burette 
with  automatic  compensator  for 
temperature  and  pressure. 


78  GAS  AND  FUEL  ANALYSIS 

sealed  at  the  bottom.  At  the  top  of  the  U  is  a  capillary  tip  which 
in  practice  is  fused  shut  as  explained  later. 

In  mounting  the  burette  which  is  assumed  to  be  clean  and 
entirely  taken  apart  the  manometer  is  connected  to  the  burette 
at  a  by  a  piece  of  good  black  rubber  tubing  wired  in  place,  and 
the  large  rubber  stopper  at  the  lower  end  of  the  burette  is  pushed 
up  until  it  rests  snugly  against  the  bottom  of  the  comparison 
tube  and  presses  the  glass  parts  at  a  firmly  together  within  the 
rubber  tube.  The  glass  water  jacket  tube  is  then  slipped  over 
the  top  of  the  burette  and  onto  the  lower  rubber  stopper  and  the 
upper  split  cork  fitted  into  place.  The  burette  is  then  placed 
in  a  stand  such  as  is  shown  in  Fig.  21.  The  levelling  bottle  is  also 
connected  to  the  burette  as  in  technical  analysis  with  the  added 
precaution  of  wiring  the  rubber  stopper  into  the  burette  so  that  it 
may  not  be  blown  out  through  the  weight  of  the  mercury  column. 
The  process  of  wiring  in  a  rubber  stopper  is  simple  but  since  begin- 
ners are  sometimes  at  a  loss  to  accomplish  it  the  following  descrip- 
tion is  given.  A  piece  of  rubber  tubing  is  first  slipped  over  the 
bottom  of  the  burette  to  give  a  soft  surface  for  the  wire  to  grip. 
A  piece  of  copper  wire  about  18  gage  is  annealed  by  passing 
several  times  through  the  flame  of  a  Bunsen  burner  and  a  piece 
about  4  in.  long  is  twisted  in  the  middle  of  one  about  8  in.  long 
to  form  a  T.  The  longer  piece  is  then  bent  around  the  burette 
and  twisted  till  it  fits  snugly.  Its  two  ends  are  now  brought 
over  the  rubber  stopper  and  twisted  with  the  free  end  of  the  4-in. 
piece  of  wire  until  the  cork  is  firmly  pressed  in. 

To  prepare  the  comparison  tube  for  use,  a  few  drops  of  water 
are  to  be  brought  into  its  lower  portion  to  saturate  the  air  it 
contains,  the  manometer  is  to  be  filled  with  mercury  and  the 
capillary  tip  is  to  be  fused  shut.  The  two  first  operations  can 
be  conveniently  accomplished  in  one  operation.  The  burette 
is  filled  with  mercury  on  whose  surface  are  a  few  drops  of  water. 
By  turning  the  stopcock  to  the  position  shown  at  D  of  Fig.  19, 
the  water  with  the  mercury  following  it  may  be  passed  through 
the  stopcock  and  the  U  tube  and  over  into  the  comparison  tube. 
The  progress  of  the  mercury  is  to  be  arrested  when  the  water 
has  trickled  down  the  comparison  tube  and  the  mercury  is  to  be 
drawn  back  until  there  is  just  enough  left  in  the  U  tube  to  fill  it 
approximately  to  the  calibration  mark  when  there  is  atmospheric 


EXACT  GAS  ANALYSIS  79 

pressure  on  both  limbs  of  the  U  as  shown  in  Fig.  19  at  A.  This 
may  be  readily  accomplished  after  one  or  two  trials.  The  cap- 
illary tip  of  the  comparison  tube  is  now  to  be  sealed  with  a  blow 
pipe  and  the  burette  is  ready  for  use. 

This  burette  has  the  advantage  over  the  usual  technical  type 
that  its  readings  are  unaffected  by  variations  in  external  tempera- 
ture and  pressure,  but  the  volumes  themselves  cannot  be  read 
more  accurately  than  with  the  technical  type  unless  a  reading 
telescope  is  employed.  Even  with  this  aid  to  the  eye  the  results 
are  not  always  certain  for  the  presence  of  a  few  drops  of  water  on 
the  mercury  alters  the  shape  and  boundaries  of  the  meniscus. 

6.  The  Bulbed  Gas  Burette  for  Exact  Analysis.— The  idea  of 
converting  the  burette  into  a  string  of  bulbs  connected  to  a  side 
arm  burette  apparently  originated  with  Bleier.1 

The  author  has  utilized  this  suggestion  in  the  design  of  the 
burette  shown  schematically  in  Fig.  20,  and  in  perspective  in 
Fig.  21 ;  it  consists  of  a  burette  with  stopcock  and  manometer 
as  already  described.  The  main  body  of  the  burette  contains 
twelve  bulbs,  each  of  a  capacity  approximating  12  c.c.  A  line  is 
etched  on  each  constriction  and  the  capacity  of  the  bulb  between 
these  marks  is  determined.  Starting  from  the  capillary  above 
the  top  bulb  a  side  arm  springs,  terminating  in  a  small  burette 
with  total  capacity  of  15  c.c.  and  graduated  in  0.1  c.c.  Both 
these  burette  tubes  connect  at  the  bottom  by  means  of  heavy 
rubber  tubes  and  a  Y  with  a  stopcock  on  each  arm,  to  a  common 
levelling  bottle.  A  screw  clamp  on  each  rubber  tube  serves  for 
the  exact  adjustment  of  the  mercury.  To  measure  a  gas,  the 
stopcock  is  placed  in  position  shown  at  C  of  Fig.  19  and  the 
mercury  in  the  bulbed  tube  brought  to  the  mark  in  one  of  the 
constricted  portions  by  opening  the  proper  stopcock  on  the  Y 
and  raising  or  lowering  the  levelling  bottle.  When  adjusted, 
the  mercury  is  held  in  its  proper  position  by  closing  the  stopcock 
on  the  Y.  The  stopcock  leading  to  the  small  burette  tube  is 
then  opened  and  the  gas  brought  to  approximately  atmospheric 
pressure  by  proper  change  in  the  mercury  level.  The  three-way 
stopcock  at  the  top  of  the  burette  tube  being  now  turned  to 
position  shown  at  D  in  Fig.  19,  the  burette  is  brought  into 
connection  with  the  manometer,  which  is  properly  set  by  further 
.  d.  Chem.  Ges.,  31,  1,  238. 


80 


GAS  AND  FUEL  ANALYSIS 


changing  the  level  of  the  mercury  in  the  small  burette.  The 
final  adjustment  in  both  burettes  is  made  by  the  screw  clamps 
on  the  rubber  tubes. 

When  the  gas  burette  is  used  in  the  manner  indicated  the  gas 
volume  is  read  under  conditions  which  are  constant  but  not 
necessarily  known.  It  is  not  usually  necessary  in  gas  analysis 


•Rubber 
Connection 


FIG.  20. — Details  of 
bulbed  gas  burette  for 
•exact  gas  analysis. 


FIG.  21. — Burette  for  exact  gas  analysis. 


to  know  the  absolute  value  of  a  gas  but  it  may  be  obtained  if  the 
temperature  and  barometric  pressure  are  noted  at  the  time  the 
tip  of  the  manometer  tube  is  sealed.  The  volume  of  the  gas  is  to 
be  read  when  the  level  of  the  mercury  in  the  two  arms  of  the  man- 
ometer is  the  same.  The  gas  has  then  the  same  volume  which  it 
would  have  had  at  the  temperature  and  pressure  prevailing 
when  the  manometer  was  sealed.  Correction  to  standard  con- 


EXACT  GAS  ANALYSIS  81 

ditions  may  be  made  mathematically  as  indicated  in  a  preced- 
ing paragraph.  This  procedure  for  reading  the  gas  volume  is 
not  as  accurate  as  the  one  recommended  for  gas  analysis  where 
the  mercury  is  brought  tangent  to  the  rim  of  a  metal  sleeve  but 
it  is  amply  accurate  for  most  purposes. 

6.  Manipulation  of  Gas  Burette  for  Exact  Analysis. — It  is 
necessary  to  discharge  from  the  burette  all  of  the  residual  gas  in- 
cluding that  in  the  manometer  tube.  This  may  be  accomplished 
by  discharging  most  of  the  gas  from  the  burette  into  the  air 
and  then  by  turning  the  stopcock  and  lowering  the  levelling 
bottle,  drawing  into  the  burette  the  gas  from  the  manometer 
until  the  mercury  of  the  U  tube  is  just  at  the  stopcock.  The 
gas  in  the  burette  may  then  be  discharged  into  the  air.  If  there 
is  danger  that  alkali  has  been  introduced  into  the  burette  in  a 
previous  operation  it  is  advisable  to  draw  into  the  burette  a  few 
cubic  centimeters  of  acidulated  water  and  with  it  rinse  down  the 
walls  of  the  entire  burette,  subsequently  expelling  it.  This  also 
makes  certain  that  the  walls  of  the  burette  are  wet  so  that  the 
gas  to  be  subsequently  introduced  will  become  saturated  with 
water. 

The  gas  is  then  introduced  into  the  burette  as  in  technical 
analysis.  If  a  volume  of  approximately  one  hundred  cubic 
centimeters  are  wanted,  nine  bulbs  are  filled  with  gas  at  atmos- 
pheric pressure.  The  stopcock  at  the  top  of  the  burette  is  then 
closed  and  the  gas  compressed  into  eight  bulbs.  Up  to  this 
time  the  side  arm  of  the  burette  has  remained  filled  with  mercury. 
The  stopcock  on  the  Y  is  now  opened  and  part  of  the  gas  trans- 
ferred to  the  side  arm  until  the  whole  is  again  under  atmospheric 
pressure  as  shown  by  the  agreement  of  the  level  of  the  mercury 
in  the  levelling  bottle  held  in  the  hand  of  the  operator,  with  the 
level  of  the  mercury  in  the  side  arm.  The  stopcock  on  the  Y  is 
now  to  be  closed  and  that  at  the  top  of  the  burette  is  to  be  turned 
to  make  communication  with  the  manometer,  the  mercury  in 
which  drops  at  once  to  approximately  its  proper  position.  By 
using  the  clamps  on  the  rubber  tubes  as  fine  adjustments  the 
meniscus  in  the  bulbed  tube  is  to  be  brought  tangent  to  the 
mark  between  two  bulbs  and  also  the  meniscus  in  the  manometer 
is  to  be  made  tangent  to  the  metal  sleeve. 

The  volume  of  the  gas  will  be  read  as  x  c.c.  in  the  bulbs  +  y 
6 


82  GAS  AND  FUEL  ANALYSIS 

c.c.  in  side  burette  +  z  c.c.  in  manometer.  As  there  are  these 
three  readings  to  be  made  it  is  necessary  that  each  be  very 
accurate.  Let  us  see  how  accurately  this  may  be  done.  First, 
the  mercury  in  the  bulbed  tube  is  to  be  brought  to  a  specified 
mark  in  a  tube  of  about  5  mm.  internal  diameter.  By  means 
of  the  screw  clamp  this  may  be  done  with  such  accuracy  that  the 
error  is  negligible.  Second,  the  volume  of  gas  in  the  side  tube 
must  be  read.  Each  0.1  c.c.  in  this  tube  occupies  a  space  of  a 
little  over  2.5  mm.  and  it  is  possible  to  interpolate  0.01  c.c.  with 
the  eye  with  an  error  of  less  than  0.02  c.c.  Third,  the  mercury 
in  the  manometer  must  be  brought  to  a  definite  mark  with  such 
exactness  that  the  barometric  pressure,  under  which  the  gas 
volume  is  read,  shall  be  almost  identical  each  time.  A  difference 
of  1  mm.  of  mercury  pressure  changes  the  gas  volume  0.13  per 
cent.,  which  on  a  volume  of  100  c.c.  equals  0.13  c.c.,  an  error  far 
too  large.  It  was  found  impracticable  to  attain  the  required 
accuracy  when  it  was  attempted  to  bring  the  mercury  to  a  mark 
etched  on  the  glass.  The  best  device  was  found  to  be  a  band  of 
thin,  blackened  copper,  wrapped  around  the  tube  and  cemented 
to  the  glass.  It  is  possible  to  bring  the  mercury  tangent  to  the 
lower  surface  of  this  with  great  exactness.  In  working  with 
this  burette  the  author  is  accustomed  to  make  all  readings  in 
duplicate,  readjusting  at  all  points  each  time,  and  to  repeat  if 
the  two  differ  from  each  other  by  more  than  0.01  c.c.  Dupli- 
cates usually  agree  within  this  limit.  The  greatest  difficulty 
found  in  manipulation  is  to  draw  the  liquid  from  the  pipette  over 
exactly  to  the  burette  stopcock  and  stop  it  there.  If  it  gets  into 
the  burette,  a  bubble  lodging  in  one  of  the  capillary  tubes  fre- 
quently damps  the  sensitiveness  of  the  manometer.  If  this 
happens  the  bubble  may  be  shot  out  of  its  lodging  place  by  com- 
pressing the  rubber  tube  above  the  screw  clamp  with  the  fingers. 
Such  a  bubble  may  also  be  carried  into  the  manometer,  where 
it  will  obscure  the  surface  of  the  meniscus.  To  remedy  this  it 
is  well  to  keep  2  or  3  mm.  of  water  on  the  surface  of  the  mercury 
in  the  manometer.  This  allows  a  perfectly  sharp  reading  of  the 
mercury  meniscus  below  the  water-level.  The  manometer 
should  respond  to  a  very  slight  movement  of  the  screw  clamp. 
The  advantages  of  this  burette  may  be  summarized  as  follows : 
It  is  a  compact  burette  which,  without  reading-telescope  or  other 


EXACT  GAS  ANALYSIS  83 

accessories,  allows  the  volume  to  be  read  with  an  error  of  less 
than  0.02  c.c.,  compensates  automatically  for  changes  of  tempera- 
ture and  pressure,  and  avoids  completely  all  errors  due  to  in- 
clusion of  air  or  loss  of  gas  in  making  connections  with  the  absorp- 
tion pipettes.  The  disadvantages  so  far  developed  are  chiefly 
those  inherent  in  all  forms  of  apparatus  which  possess  a  stopcock 
and  rubber  connections.  Both  may  leak;  but  on  the  other  hand 
both  may  be  kept  so  tight  for  limited  periods  of  time  as  to  in- 
troduce no  measurable  error. 

7.  Calibration  of  Burette. — The  burette  must  be  carefully 
calibrated  throughout  its  entire  length.  This  can  best  be  done  by 
weighing  the  mercury  discharged.  One  cubic  centimeter  of  mer- 
cury at  0°  C.  weighs  13.59  grm.  Since  all  that  is  desired  is  a 
relative  calibration  the  mercury  need  not  be  strictly  pure  nor 
need  correction  be  made  for  its  temperature.  Ten  milligrams 
of  mercury  corresponds  to  less  than  one-thousandth  of  a  cubic 
centimeter  so  greater  accuracy  than  this  in  weighing  is  a  waste  of 
time.  Wire  a  stopper  carrying  a  stopcock  into  the  bulbed  tube 
and  fasten  by  a  stiff  rubber  tube  a  stopcock  to  the  side  arm.  It 
is  especially  important  that  the  rubber  tubing  should  not  bulge 
under  the  mercury  pressure  and  to  prevent  this  it  should  be  firmly 
wound  with  wire.  Connect  the  tips  of  these  stopcocks  to  the 
mercury  levelling  bottle  and  through  them  fill  the  burette  with 
mercurj'  completely  to  the  stopcock.  The  portion  first  calibrated 
is  the  capillary  tube  from  the  bottom  of  the  stopcock  to  the  zero 
of  the  bulbed  tube  and  the  zero  of  the  side  arm.  After  that  each 
bulb  and  each  cubic  centimeter  of  the  side  arm  is  separately 
calibrated.  The  accuracy  of  the  calibration  may  be  checked  by 
the  procedure  of  a  regular  analysis  where  a  volume  of  gas  is  chosen 
such  that  it  for  instance  fills  9  bulbs  and  a  small  portion  of  the  side 
arm.  The  method  of  reading  may  then  be  changed  to  eight  bulbs 
plus  a  considerable  volume  in  the  side  arm  but  if  the  calibration  is 
correct  the  same  volume  should,  of  course,  be  shown.  The  vol- 
ume of  the  small  portion  of  the  manometer  tube  above  the  mer- 
cury may  best  be  determined  by  filling  the  burette  completely 
with  mercury  and  then  drawing  the  air  out  of  the  manometer 
tube  into  the  side  arm  of  the  burette  where  it  may  be  measured 
under  atmospheric  pressure  with  an  error  of  a  few  tenths  of  a  per 


84  GAS  AND  FUEL  ANALYSIS 

cent.     Since  the  total  volume  is  only  a  small  fraction  of  a  cubic 
centimeter  the  method  is  amply  accurate. 

8.  Absorption  Methods  in  Exact  Gas  Analysis — The  same 
reagents  may  in  general  be  used  in  exact  as  in  technical  analysis. 
Care  should  however  be  taken  to  see  that  the  reagent  has  been 
recently  saturated  with  gas  of  a  sort  similar  to  that  which  is  to  be 
analyzed.     In  case  the  reagent  is  one  which  does  not  attack  mer- 
cury the  pipette  is  to  be  filled  with  mercury  which  carries  on  its 
surface  only  a  few  cubic  centimeters  of  the  reagent.     If  pipettes 
of  the  ordinary  type  are  filled  with  mercury  the  mercury  rising 
in  the  second  bulb  places  the  gas  under  considerable  pressure  and 
greatly  increases  the  danger  of  leakage  at  the  rubber  connections. 
An  explosion  pipette  may  with  advantage  be  used  as  an  absorption 
pipette  under  these  circumstances  since  its  stopcock  and  levelling 
bottle  allow  a  regulation  of  the  pressure  within  the  pipette. 
Where  the  greatest  accuracy  is  not  required  it  is  sufficient  to  lessen 
the  errors  due  to  diffusion  by  introducing  a  few  cubic  centimeters 
of  mercury  to  form  a  seal  in  the  ordinary  form  of  pipette.     In 
the  case  of  solutions  like  cuprous  chloride  where  mercury  cannot 
be  used  reliance  must  be  placed  on  the  complete  saturation  of  the 
reagent.     Where  gases  are  readily  soluble  errors  due  to  diffusion 
mount  up  rapidly.     For  instance :  A  sample  of  74  c.c.  of  acetylene 
gas  when  passed  into  an  ordinary  NaOH  pipette  as  used  in  tech- 
nical gas  analysis  decreased  to  63.9  after  quietly  standing  for  three 
minutes,  to  58.0  after  a  second  contact,  and  to  29.0  c.c.  after  three 
minutes  shaking  with  the  same  reagent.     After  two  more  similar 
periods  the  residue  left  in  the  burette  was  only  5.2  c.c.     A  second 
sample  of  gas  behaved  similarly,  and  by  connecting  a  burette 
with  the  second  bulb  of  the  pipette  the  acetylene  diffusing  through 
was  recovered  quantitatively. 

9.  Carbon  Dioxide. — Carbon  dioxide  is  usually  estimated  by 
absorption  in  caustic  soda  as  in  technical  analysis.     If  other 
acid  gases  such  as  H2S,  S02,  or  HC1  are  present  they  may  be  re- 
moved by  first  shaking  the  gas  in  a  pipette  containing  KMn04 
very  faintly  acidified  with    H2S04.    An  increase    in   volume 
after    this   operation  would    indicate   that   oxygen   had   been 
evolved  during  the  process.     If  direct  evidence  of  the  presence  of 
CO2  is  desired  a  clear  solution  of  Ba(OH)2  should  be  used  instead 
of  NaOH  in  the  pipette  for  CO2  absorption.     The  formation  of  a 


EXACT  GAS  ANALYSIS  85 

white  precipitate  completely  soluble  in  HC1  will  show  the  presence 
of  carbonates. 

10.  Unsaturated  Hydrocarbons. — Unsaturated  hydrocarbons 
as  a  class  are  estimated  as  in  technical  gas  analysis  by  absorption 
with  fuming  sulphuric  acid  or  bromine  water.  It  is  difficult  to 
prevent  the  errors  due  to  diffusion  mentioned  in  §  8  since  both 
reagents  attack  mercury.  Where  it  is  desirable  to  eliminate  the 
error  as  far  as  possible  a  stopcock  may  be  placed  in  the  line  be- 
tween the  two  bulbs  of  the  pipette  which  can  be  closed  after  the 
gas  has  been  passed  into  the  pipette  while  absorption  is  taking  place. 

A  separation  of  the  constituent  Unsaturated  hydrocarbons  is 
rarely  carried  out.  It  is  best  accomplished  by  bubbling  a  known 
volume  of  the  gas  through  bromine  and  fractionating  the  resulting 
bromides.  The  results  are  at  best  unsatisfactory.  Ernshaw1 
has  shown  that  it  is  possible  to  calculate  the  average  composition 
of  the  illuminants  from  data  obtained  by  exploding  a  sample  of 
the  gas  which  still  contains  the  olefines  and  deducting  from  the 
observed  contraction  and  carbon  dioxide  the  amounts  due  to 
hydrogen,  carbon  monoxide  and  the  paraffines.  The  method  de- 
mands very  accurate  work. 

Acetylene  may  be  absorbed  in  a  faintly  ammoniacal  solution  of 
silver  or  copper  salts.  The  precipitated  acetylides  are  explosive 
and  care  should  be  taken  in  handling  them.  The  ammonia 
vapors  are  to  be  removed  from  the  gas  by  shaking  with  dilute 
acid  before  the  volume  is  measured.  Water  dissolves  more  than 
its  own  volume  of  acetylene,  so  great  care  must  be  exercised 
to  saturate  the  water  of  containing  vessels  before  the  gas  to  be 
analyzed  is  brought  into  them.  Also  gas  from  which  large  per- 
centages of  acetylene  have  been  removed  must  not  be  returned  to 
vessels  containing  much  water  with  which  it  had  previously  been 
in  equilibrium  since  the  water  will  give  back  to  the  gas  material 
amounts  of  acetylene. 

Phosphorus  forms  a  delicate  reagent  for  qualitative  detection 
of  traces  of  Unsaturated  hydrocarbons.  If  when  the  gas  in 
question  is  brought  in  contact  with  phosphorus  under  the  con- 
ditions prescribed  for  the  estimation  of  oxygen,  white  fumes 
form,  it  is  certain  evidence  of  the  absence  of  more  than  minute 
traces  of  Unsaturated  hydrocarbons.  If  on  the  other  hand  the 

1  Jour.  Franklin  Inst.,  146,  161  (1898). 


86  GAS  AND  FUEL  ANALYSIS 

fumes  fail  to  appear  even  after  the  addition  of  air  it  is  not  abso- 
lutely certain  that  the  poison  is  an  unsaturated  hydrocarbon  for 
ether,  chloroform  and  a  number  of  other  substances  behave 
similarly. 

11.  Oxygen.  —  The  estimation  of  oxygen  by  phosphorus  as  in 
technical  analysis  admits  of  little  improvement  in  simplicity  or 
accuracy.     Alkaline  pyrogallate  may  be  used  where  it  is  not 
possible  to  remove  the  poisons  which  prevent  the  use  of  phos- 
phorus, and  the  ammoniacal  copper  reagent  may  be  used,  subject 
to  the  limitations  given  in  Chapter  III. 

12.  Carbon  Monoxide.  —  It  was  stated  in  Chapter  III  that  the 
methods  for  estimation  of  carbon  monoxide  were  unsatisfactory. 
They  are  more  unsatisfactory  for  exact  than  for  technical  anal- 
ysis.    The  absorption  by  cuprous  chloride  given  in  technical 
methods  is  hardly  to  be  considered  as  an  accurate  method.     The 
change  in  the  absorption  spectrum  of  blood  after  treatment  with 
carbon  monoxide  may  be  made  an  accurate  qualitative  test  for 
carbon  monoxide  but  does  not  lend  itself  readily  to  quantitative 
purposes. 

The  method  usually  employed  is  to  oxidize  the  carbon  monox- 
ide, after  having  made  certain  that  all  other  compounds  which 
would  be  affected  by  the  oxidizing  agent  have  been  removed. 

Iodine  pentoxide  is  the  most  commonly  employed  oxidizing 
agent,  the  reaction  being: 


The  details  here  given  are  essentially  those  of  Kinnicutt  and 
Sanford,1  who  used  substantially  the  method  of  Nicloux.  The 
gas  is  first  purified  by  being  bubbled  slowly  through  concen- 
trated sulphuric  acid  and  then  passed  through  a  tube  contain- 
ing lumps  of  caustic  soda.  This  treatment  removes  unsatu- 
rated hydrocarbons,  hydrogen  sulphide,  sulphur  dioxide  and 
similar  reducing  gases.  The  purified  gas  is  then  passed  through 
iodine  pentoxide  contained  in  a  U  tube  immersed  in  an  oil  bath 
at  150°  C.  Following  the  U  tube  comes  another  absorption 
tube  containing  about  0.5  g.  potassium  iodide  dissolved  in  10  c.c. 
of  water.  If  a  liter  of  gas  is  used  as  small  an  amount  as  0.025 
c.c.  of  carbon  monoxide  may  be  detected.  The  method  is  ordi- 
lJour.  Am.  Chem.  Soc.,  22,  15  (1900). 


EXACT  GAS  ANALYSIS  87 

narily  only  used  for  the  detection  of  minute  amounts  of  carbon 
monoxide  and  it  is  not  suitable  for  large  amounts.  The  absence 
of  any  liberated  iodine  may  be  considered  a  positive  proof  of  the 
absence  of  carbon  monoxide.  The  liberation  of  iodine  is  how- 
ever only  a  proof  that  some  reducing  substance  was  present, 
which  can  only  with  certainty  be  claimed  as  carbon  monoxide 
after  careful  blank  tests  have  shown  that  the  purifying  train  is 
adequate  to  remove  all  other  reducing  substances  and  that  the 
iodine  pentoxide  does  not  yield  iodine  except  in  the  presence  of 
such  a  reducing  substance.  Gill  and  Bartlett1  tested  this  method 
on  illuminating  gas  and  report  results  about  9  per  cent.  high. 
They  report  accurate  results  when  mixtures  of  carbon  monoxide 
and  air  are  used. 

Morgan  and  McWhorter2  traced  some  of  the  difficulties  of 
this  method  to  the  reduction  of  the  iodine  pentoxide  by  the  hydro- 
carbon vapors  given  off  by  the  lubricant  and  in  the  stopcocks  of 
the  U  tube  containing  it.  They  recommend  that  the  tips  of  the 
U  tube  be  sealed  with  a  flame.  They  further  recommend  the 
estimation  of  the  carbon  dioxide  formed  in  the  reaction  as  a 
more  accurate  index  of  the  carbon  monoxide  than  is  the  iodine. 
They  insert  an  absorption  tube  containing  standard  barium  hy- 
droxide in  the  train  after  the  tube  containing  potassium  iodide 
and  after  the  close  of  the  test  titrate  the  residual  barium  hydrox- 
ide with  oxalic  acid. 

13.  Hydrogen. — Hydrogen  may  be  directly  absorbed  in 
metallic  palladium  but  is  almost  always  oxidized.  The  gas 
should  first  be  freed  from  unsaturated  hydrocarbons  and  other 
reducing  gases  as  well  as  oxygen,  so  that  it  contains  only  hydro- 
gen, saturated  hydrocarbons  and  nitrogen.  There  is  then  a  choice 
of  methods — one  class  oxidizing  the  hydrogen  without  affecting 
the  hydrocarbons,  and  the  other  simultaneously  oxidizing  both 
hydrogen  and  hydrocarbons. 

There  are  several  methods  for  fractional  oxidation  of  hydrogen 
which  are  reliable.  .The  errors  which  attend  the  method  of 
simultaneous  oxidation  of  hydrogen  and  methane  have  been 
briefly  discussed  in  Chapter  IV.  The  important  systematic 
error  in  explosions  and  flame  combustions  is  due  to  the  oxidation 

1  J.  Am.  Chem.  Soc.,  29,  1589  (1907). 

2  Jour.  Ind.  and  Eng.  Chem.,  2,  9  (1910). 


88 


GAS  AND  FUEL  ANALYSIS 


of  nitrogen.  The  formation  of  oxides  of  nitrogen  increases  with 
higher  temperatures.  The  most  favorable  mixture  for  their 
formation  is  one  in  which  there  are  equal  volumes  of  oxygen  and 
nitrogen.  The  errors  are  therefore  minimised  by  keeping  the 
temperature  of  combustion  low  and  by  making  the  diluting  gas 
as  nearly  pure  oxygen  as  possible.  It  is  not  possible  to  give  an 
absolute  statement  of  the  magnitude  of  the  error  introduced  for 
it  will  vary  with  each  difference  in  the  form  of  the  explosion 
vessel  and  in  the  violence  of  the  explosion.  The  following 
series  of  measurements  by  the  author1  will  indicate  the  magnitude 
of  the  error  and  also  the  accuracy  of  the  burette  for  exact  gas 
analysis  described  in  this  chapter. 

EXPLOSION  OF  PURE  HYDROGEN 


Hydrogen, 
c.c. 

Air, 
c.c. 

Contraction 
after  explo- 
sion, c.c. 

Calculated 
per  cent, 
hydrogen 

Contraction 
over  potas- 
sium hydrox- 
ide, c.c. 

Explo- 
sive 
ratio 

11.35 

84.80 

16.90 

99.26 

0.00 

4.64 

12.11 

85.57 

18.08 

99.53 

0.00 

4.37 

14.19 

84.27 

21.27 

99.92 

0.00 

3.62 

16.77 

85.77 

25.13 

99.90 

0.01 

3.06 

16.54 

82.64 

24.76 

99.80 

0.01 

3.00 

18.19 

83.22 

27.29 

100.01 

0.01 

2.71 

21.10 

83.28 

31.74 

100.28 

0.00 

2.29 

27.04 

83.86 

40.80 

100.59 

0.11 

1.73 

The  hydrogen  was  prepared  by  the  action  of  caustic  potash 
on  aluminium  so  as  to  be  free  from  hydrocarbons.  It  will  be 
noted  that  in  this  series  air  was  used  to  supply  the  oxygen  and 
as  the  diluent.  A  variation  of  1.3  per  cent,  in  the  apparent 
purity  of  hydrogen  due  solely  to  errors  inherent  in  the  explosion 
process  makes  it  evident  that  the  method  can  hardly  be  called 
an  accurate  one. 

The  errors  attendant  upon  the  flame  combustion  method  of 
Dennis  and  Hopkins  described  in  §  9  of  Chapter  IV  are  illustrated 
in  the  following  series. 

COMPARISON  OP  EXPLOSION  AND  COMBUSTION  METHODS 
ON  HYDROGEN 

Explosions  with  Air 


Sample 
hydrogen 
c.c. 

Air 
c.c. 

Contraction 
after  explo- 
sion, c.c. 

Contraction 
over  potassium 
hydroxide,  c.c. 

Hydrogen 
per  cent. 

Explo- 
sive 
ratio 

15.32 
18.15 

85.34 
82.39 

22.71 
26.93 

0.04 
0.06 

98.82 
98.91 

3.43 
2.73 

A  *1  f*      f  1  C\(\  1   \ 


EXACT  GAS  ANALYSIS 
Explosions  with  Oxygen 


89 


Sample 
hydrogen 
c.c. 

Air 
c.c. 

Contraction 
after  explo- 
sion, c.c. 

Contraction 
over  potassium 
hydroxide,  c.c. 

Hydrogen 
per  cent. 

Explo- 
sive 
ratio 

Oxygen  I 


14.82 

93.51 

22.04 

0.02 

99.14 

3.91 

16.48 

82.18 

24.51 

0.02 

99.15 

3.02 

20.58 

80.09 

30.60 

0.03 

99.12 

2.29 

Combustions  by  the  Dennis  and  Hopkins  Method 


Hydrogen 
c.c. 

Oxygen 
c.c. 

Air 
c.c. 

Contraction 
after  com- 
bustion, c.c. 

Contraction 
over  potassium 
hydroxide,  c.c. 

Hydro- 
gen 
per  cent. 

Oxygen 
in  excess 

91.29 

58.48 
89.31 

51.65 
53.39 
40.77 

54.55 
50.14 
50.21 

136.72 
87.43 
133.57 

0.04 
0.10 
0.07 

99.84 
99.66 
99.70 

13.72 
40.89 
3.73 

The  values  obi  ained  by  explosion  with  oxygen  are  remarkably 
concordant  and  are  probably  as  accurate  as  we  can  hope  to 
attain.  The  values  obtained  by  explosion  with  air  are  higher 
and  more  irregular.  The  values  of  the  Dennis  and  Hopkins 
method  are  also  high  and  involve  an  error  of  about  0.6  per  cent. 

14.  Methane. — There  are  no  absorption  methods  for  methane 
which  are  acceptable.  It  is  estimated  by  oxidation  to  CO2  and 
H2O  with  measurement  of  the  change  in  volume  after  oxidation 
and  after  absorption  of  the  CO2.  The  general  methods  are 
given  in  §  7  to  11  of  Chapter  IV.  There  is  greater  liability  of 
error  in  the  explosion  process  through  formation  of  oxides  of 
nitrogen  than  is  the  case  with  hydrogen,  as  is  illustrated  by  the 
following  series  of  tests  of  methane  made  from  methyl  iodide 
and  the  zinc  copper  couple. 

EXPLOSION  OF  METHANE 


Sample 
methane 
c.c. 

Air 
c.c. 

Contrac- 
tion after 
explosion 

Carbon 
dioxide 
c.c. 

Methane 
per  cent. 

Hydro- 
gen per 
cent. 

Explo- 
sive 
ratio 

Ratio 
contrac- 
tion 

sample 

7.05 
8.93 
9.07 
10.20 

92.07 
104.17 
98.35 
98.22 

13.09 
16.66 
17.10 
19.27 

6.53 
8.31 
8.54 
9.63 

92.62 
93.28 
94.15 
94.41 

0.28 
0.14 
0.14 
0.06 

4.05 
3.53 
3.19 
2.61 

1.85 
1.86 

1.88 
1.89 

90  GAS  AND  FUEL  ANALYSIS 

In  these  experiments  the  explosive  ratios  all  lie  within  the 
limits  set  by  Bunsen,  but  there  is  a  variation  of  1.6  per  cent,  in 
the  apparent  percentage  of  methane  as  calculated  by  the  usual 
methods  and  there  is  a  corresponding  variation  in  the  amount  of 
hydrogen.  Similar  experiments  made  with  commercial  oxygen 
(96.5  per  cent,  pure)  as  the  diluting  agent  instead  of  air  showed 
errors  rather  greater  than  when  using  air  in  similar  amount. 
The  greater  error  in  analyzing  methane  as  compared  with  hydro- 
gen results  almost  certainly  from  the  higher  temperatures  at- 
tained in  the  explosion  of  methane.  It  is  not  possible  to  dilute 
the  gas  sufficiently  to  avoid  this  danger  without  running  the 
risk  of  incomplete  combustion  of  the  methane.  The  methods  of 
oxidation  of  methane  which  involve  flame  as  in  explosion  or  the 
Dennis  and  Hopkins  method  are  always  liable  to  material  error 
due  to  formation  of  oxides  of  nitrogen.  The  errois  may  be  mini- 
mized by  keeping  the  gases  at  a  low  temperature  while  reacting. 
Jaeger's  method  of  analysis  by  combustion  wilh  copper  oxide 
in  a  combustion  tube  as  described  in  §  11  of  Chapter  IV  cannot 
involve  the  formation  of  material  amounts  of  oxides  of  nitrogen. 
This  method  is  not  so  rapid  or  convenient  as  the  others  but,  if 
care  is  taken  to  carefully  cool  the  gas,  including  that  remaining  in 
the  combustion  tube,  to  its  initial  temperature  before  noting  the 
change  in  volume,  it  is  believed  to  be  the  most  accurate  method. 

15.  Errors  in  Calculation  of  Results  of  Explosion  and  Com- 
bustion.— Some  gases,  notably  carbon  dioxide  and  the  complex 
hydrocarbons,  do  not  conform  completely  to  the  gas  laws.  The 
deviation  is  slight  at  low  partial  pressure  and  is  usually  negligible, 
but  should  be  discussed.  Burrill  and  Seibert1  cite  the  following 
instances.  If  the  volume  relations  in  the  explosion  of  methane 
and  oxygen  are  accurately  expressed  they  will  be  written  as 
follows : 

0.999  CH  4+ 2.000  02  =  0.995  C02+(2H20  which  condenses) 

According  to  the  above  equation  if  perfectly  pure  methane  were 
exploded  with  pure  oxygen  the  composition  as  calculated  from 
the  contraction  would,  if  calculated  by  the  usual  rules,  be  100.2 
per  cent.,  while  if  calculated  from  the  carbon  dioxide  its  percent- 
age would  be  99.4  per  cent.  The  following  table  shows  the 
1  Bui.  42,  Bureau  of  Mines. 


EXACT  GAS  ANALYSIS  91 

molecular  volumes  for  carbon  dioxide  at  20°  C.  and  different 
partial  pressures: 

Mm.  of  mercury  Molecular  vol. 

100  0.9993 

200  0.9986 

300  0.9980 

400  0.9972 

500  0.9965 

600  0.9958 

700  0.9951 

760  0 . 9950 

If  methane  should  be  exploded  with  the  theoretical  volume  of 
air  instead  of  pure  oxygen  the  error  would  decrease  so  that  the 
apparent  purity  as  calculated  from  the  contraction  would  be 
100.14  per  cent,  and  as  calculated  from  the  carbon  dioxide  would 
be  99.86.     These  errors  are  in  general  within  the  limits  of  the 
other  errors  arising  in  analysis  by  explosion  or  combustion. 
Where  ethane  is  present  the  error  is  greater 
0.990  C2H6+3.500  O2  =  1.988  C02+(3H20  which  condenses) 
The  molecular  volumes  of  ethane  corresponding   to   different 
partial  pressures  are  shown  in  the  following  table: 

Mm.  of  mercury  Molecular  vol. 

0  1.000 

100  0.999 

200  0.997 

300  0.996 

400  0.995 

500  0.993 

600  0.992 

700  0.991 

760  0.990 

Burrell  and  Seibert  cite  an  analysis  of  Pittsburgh  natural  gas 
which,  calculated  from  the  theoretical  equations,  showed  15.1 
per  cent.  C2H6  and  84.1  per  cent.  CH4,  while  by  calculation  from 
the  corrected  equations  the  results  became  15.7  per  cent.  C2H6 
and  83.1  per  cent.  CH4. 

16.  Nitrogen. — The  method  of  removal  of  all  gases  except 
nitrogen  by  combustion  with  copper  oxide  as  given  in  §  12  of 
Chapter  IV  is  fairly  exact.  The  gases  of  the  argon  group  are 
left  with  the  nitrogen  but  the  separation  of  these  is  not  included 
in  this  work. 


CHAPTER  VII 
HEATING  VALUE  OF  GAS 

1.  Introduction. — The  heating  value  of  gases  may  be  deter- 
mined by  combustion  in  a  bomb  calorimeter  but  the  difficulty 
of  transferring  a  definite  quantity  of  gas  to  the  bomb  prevents 
the  general  adoption  of  such  a  method.     The  standard  type  of 
calorimeter  is  one  in  which  the  gas  is  burned  with  atmospheric 
air  and  the  total  heat  of  the  products  of  combustion  is  transferred 
as  completely  as  possible  to  the  water  of  the  calorimeter.     A 
continuous  flow  calorimeter  is  usually  employed  wherever  a  suf- 
ficient amount  of  gas  is  available,  but  the  intermittent  type  is 
also  used.     In  some  other  types  of  calorimeter  the  heat  of  com- 
bustion is  used  to  raise  the  temperature  of  a  piece  of  metal,  or  a 
thermocouple  placed  in  the  flame.     Calorimeters  of  these  latter 
types  give  merely  relative  figures  which  can  only  be  converted 
into  heat  values  after  very  careful  calibration.     They  are  in 
no  sense  standard  instruments  and  are  not  discussed  in  this  book. 
It  is  also  possible  to  calculate  the  heating  value  of  the  gas  from 
its  chemical  composition  with  approximate  accuracy. 

2.  Continuous    Flow    Calorimeters. — The    continuous     flow 
calorimeter  bears  much  resemblance  to  the  type  of  instantaneous 
water  heaters  found  in  bath  rooms.     The  gas,   after  passing 
through  a  meter,  is  burned  in  a  Bunsen  burner.     The  products  of 
combustion  give  up  their  heat  to  a  stream  of  cold  water  flowing 
in  a  direction  opposite  to  that  of  the  gases  so  that  the  gases 
emerge  from  the  instrument  cold  and  the  water  emerges  hot. 

The  process  to  be  accurate  requires  the  fulfillment  of  the  follow- 
ing conditions: 

a.  The  gases  must  be  accurately  measured,  be  burned  at  a 
constant  rate,  and  combustion  must  be  complete. 

b.  The  water  must  enter  at  a  constant  rate  and  at  constant 
temperature,  and  be  at  approximately  room  temperature. 

c.  The  heat  of  combustion  must  all  be  transmitted  to  the 

92 


HEATING  VALUE  OF  GAS  93 

water  whose  mass  and  rise  in  temperature  must  be  accurately 
determined. 

The  pioneer  instrument  of  this  type  was  that  devised  by  F.  W. 
Hartley  in  1884. l  The  standard  by  which  gas  was  judged  was, 
at  that  time,  candle  power  and  therefore  the  instrument  did  not 
attract  much  attention.  The  first  calorimeter  to  be  used  widely 
was  that  designed  in  1893  by  Hugo  Junkers.2 

3.  Wet  Gas  Meters. — The  gas  is  usually  measured  in  a  wet 
meter  which  consists  of  a  horizontal  cylindrical  casing  of  sheet 
metal  enclosing  a  horizontal  drum  and  filled  about  half  full  of 
water.  The  drum  is  divided  with  slant  partitions  into  three  or 
four  compartments,  each  with  its  own  entrance  for  gas  at  the 
back  and  its  exit  at  the  front.  Each  of  these  compartments  con- 
stitutes a  distorted  screw  thread  enlarged  to  a  chamber  in  the 
center.  As  the  inlet  of  one  of  these  compartments  comes  out  of 
the  water  the  pressure  of  the  gas  entering  causes  the  drum  to 
revolve  and  the  compartment  fills  with  gas.  When  the  compart- 
ment is  full  the  inlet  dips  below  the  water  and  seals,  the  outlet 
unseals  and  the  water  entering  the  compartment  drives  out  the 
gas  before  it.  If  there  were  only  one  or  two  compartments  the 
flow  of  gas  could  not  be  continuous,  but  with  three  or  four  com- 
partments in  the  drum,  one  is  always  discharging  and  the  rate  of 
flow  of  gas  is  about  constant. 

It  will  readily  be  seen  that  the  capacity  of  each  compartment 
and  the  time  of  sealing  and  unsealing  the  inlet  and  outlet  will 
be  affected  by  the  height  of  water  in  the  meter  so  that  the  exact 
setting  of  the  water  level  becomes  of  great  importance.  Each 
meter  is  provided  with  a  gage  glass  and  a  pointer  which  can  be 
adjusted  to  indicate  the  proper  water  level.  The  Committee  on 
Calorimetry  of  the  American  Gas  Institute  in  its  1912  report 
states  that  even  with  careful  work  an  error  of  0.3  per  cent,  may 
be  introduced  by  inaccurate  adjustment  of  the  water  level  and 
that  on  passing  100  cubic  feet  of  gas  through  the  meter  an  error  of 
about  equal  magnitude  may  be  introduced  through  evaporation 
of  the  water.  The  meter  must  be  calibrated  frequently  for  accu- 
rate work. 

The  gas  meter  must  be  calibrated  by  passing  a  known  volume 

1  London  Jour.  Gas  Lighting,  43,  1142  (1884). 

2  Jour,  fur  Gasbel,  36,  81  (1898). 


94  GAS  AND  FUEL  ANALYSIS 

of  gas  through  it.  This  known  volume  may  most  accurately 
be  obtained  by  the  use  of  what  is  known  as  a  cubic  foot  bottle  or  a 
smaller  container  of  the  same  type.  Containers  of  this  type 
should  be  rigidly  made  of  glass  or  metal  and  tapered  at  the  top 
and  bottom  to  glass  tubes  of  small  diameter  upon  which  zero 
marks  are  etched.  The  capacity  of  one  of  these  containers  is 
determined  by  the  weight  of  water  which  it  contains.  They  may 
be  bought  in  elaborate  forms  and  with  the  certificate  of  the 
Bureau  of  Standards.  Where  a  standardized  bottle  is  not  avail- 
able a  sufficiently  accurate  substitute  may  be  improvised  from  a 
gas  holder  of  the  type  shown  in  Fig.  23.  This  consists  of  a  cy- 
linder of  galvanized  iron  coned  and  terminated  with  a  cock  at 
both  ends.  If  this  is  filled  with  water  at  room  temperature  and 
weighed,  and  then  drained  and  weighed,  the  volume  of  the  tank 
may  be  calculated  from  the  following  table.  The  volume  thus 
obtained  may  be  considered  constant  within  ordinary  ranges  of 
temperature  since  the  coefficient  of  expansion  of  mild  steel  is 
only  0.0000067  per  degree  Fahrenheit. 

The  tank  shown  in  the  illustration  holds  one-third  of  a  cubic 
foot  and  is  weighed  upon  the  balance  shown  in  front  of  it.  If 
larger  tanks  are  used  they  must  be  made  of  heavy  material  so  as 
not  to  change  in  volume  when  filled  with  water. 

WEIGHT  OF  ONE  CUBIC  FOOT  OF  WATER 

50°  F , 62.41  Ib. 

60°  F 62.371b. 

70°  F 62.31  Ib. 

80°  F 62.231b. 

90°  F 62,131b. 

In  making  the  test  the  tank  is  to  be  filled  absolutely  full  of 
water  of  almost  room  temperature  and  left  standing  by  the  side 
of  the  meter  in  a  room  of  fairly  constant  temperature  for  several 
hours  to  make  sure  that  all  the  parts  of  the  system  are  at  the 
same  temperature.  The  gas  supply  is  to  be  bubbled  through 
water  in  order  to  be  certain  that  it  is  saturated  with  water  vapor. 
If  the  depth  of  water  in  the  saturator  is  so  adjusted  that  no  gas 
bubbles  through  unless  a  very  slight  suction  is  applied,  it  will 
obviate  mathematical  corrections,  because  if  the  static  pressure 


HEATING  VALUE  OF  GAS  95 

of  the  water  in  the  saturator  is  adjusted  to  counterbalance  the 
pressure  of  the  incoming  gas,  and  the  outlet  of  the  discharge 
from  the  tank  is  set  at  the  level  of  the  lower  cock,  a  direct  com- 
parison of  the  volume  of  gas  registered  by  the  meter  and  the 
capacity  of  the  tank  gives  the  calibration  factor  for  the  meter 
without  any  calculation  for  difference  in  pressure.  So  long  as  the 
whole  system  is  at  the  same  temperature  it  is  immaterial  what  the 
temperature  is.  The  upper  cock  of  the  tank  may  now  be  con- 
nected directly  to  the  outlet  of  the  meter.  The  lower  cock  of  the 
tank  should  have  a  rubber  tube  attached  which  drops  down  to 
allow  the  formation  of  a  water  seal  and  rises  again  to  discharge  the 
water  at  the  level  of  the  cock.  If  now  the  lower  cock  on  the  tank 
is  opened  water  will  flow  out  through  the  rubber,  tube  and  an 
equal  volume  of  gas  will  flow  through  the  meter.  When  the 
water  is  all  out  of  the  tank  the  gas  will  be  automatically  stopped 
by  the  water  seal  in  the  rubber  outlet  tube  and  the  whole  system 
will  be  under  atmospheric  pressure,  which  is  a  condition  neces- 
sary for  accurate  work. 

4.  Corrections  for  Temperature  and  Pressure. — The  volume 
of  the  gas  used  in  a  test  must  be  corrected  for  temperature  and 
pressure.  The  standard  conditions  for  the  United  States  and 
Great  Britian  are  a  temperature  of  60°  F.  and  a  barometric 
pressure  of  30  in.  of  mercury.  The  gas  as  it  comes  from  the  wet 
meter  is  assumed  to  be  saturated  with  water  and  correction  is 
made  for  the  excess  of  water  vapor  over  that  normal  for  60°. 
Tables  giving  the  correction  factors  in  convenient  form  have  been 
issued  by  the  Gas  Referees  of  London.  They  are  derived  accord- 
ing to  the  formula. 

=  17.64(h-a) 
460+t 

where  n  =  factor  sought 

h  =  height  of  barometric  column  in  inches  mercury 
a  =  vapor  tension  in  inches  of  mercury  at  temp,  t 
t  =  observed  temp,  of  meter  in  degrees  F. 

Although  this  formula  apparently  involves  the  full  correction 
for  vapor  tension  which  would  reduce  the  volume  of  gas  to  a  dry 
basis  at  60°  F.,  there  is  a  further  correction  contained  in  the  figure 


96  GAS  AND  FUEL  ANALYSIS 

17.64  of  the  formula  which  corrects  the  gas  to  a  basis  of  60°  F. 
when  saturated  with  water.     The  full  formula  is  as  follows; 


W     30     \ 
/  \30-.517 


The  first  member  of  the  formula  corrects  the  volume  to  32°  F., 
the  second  to  60°  F.,  the  third  to  dry  gas  under  30  in.  barometric 
pressure,  and  the  fourth  to  gas  saturated  with  moisture  at  60° 
F.  the  0.51  being  the  vapor  pressure  of  water  at  60°  F.  Table 
III  in  the  Appendix  gives  the  factors  for  each  degree  Fahrenheit 
and  each  0.1  in.  pressure  within  wide  limits. 

5.  Control  of  the  Water. — The  water  supply  must  always  be 
sufficient  to  keep  the  overflow  on  the  small  elevated  constant- 
level  tank  in  operation.     If  the  supply  of  water  to  the  tank 
slackens  much  the  rate  of  flow  to  the  calorimeter  will  also  change. 
The   temperature   of  the  water  should   also  be   constant   and 
approximately  that  of  the  room.     In  .order  to  insure  a  water 
supply  of  even  temperature  and  pressure  it  is  advisable  to  install 
in  the  calorimeter  room  an  elevated  tank  of  at  least  20  gallons 
capacity  connected  to  the  water  mains  and  provided  with  an  over- 
flow from  which  the  supply  for  the  calorimeter  is  drawn. 

6.  Measurement  of  Temperature. — The  temperature  of  the 
inflowing  and  outgoing  water  is  determined  by  thermometers 
which  should  read  to  tenths  of  a  degree.     They  must  be  carefully 
calibrated  throughout  their  length  by  comparison  with  a  stand- 
ard.    It  is  immaterial  whether  they  are  Centigrade  or  Fahrenheit 
thermometers  but  the  Fahrenheit  are  more  convenient,  when  as 
is  customary,  the  results  >are  to  be  expressed  in  British  thermal 
units  per  cubic  foot  of  gas.     The  thermometers  are  to  be  carefully 
placed  in  the  calorimeter  so  that  their  bulbs  are  completely  sur- 
rounded by  water  and  are  nowhere  in  contact  with  the  metal  of 
the  calorimeter. 

7.  Measurement   of   Mass   of  Water. — The   mass   of   water 
heated  during  an  experiment  may  be  determined  either  by  meas- 
urement or  by  weight.     A  2000-c.c.  graduated  cylinder  is  used 
sometimes.     This  is  not  an  ideal  device,  for  not  only  are  the 
graduations  coarse  but  the  varying  temperatures  at  which  the 


HEATING  VALUE  OF  GAS  97 

water  is  measured  necessitate  the  use  of  different  correction 
factors  to  reduce  the  volumes  to  the  equivalent  weights.  It  is 
much  more  satisfactory  to  weigh  the  water.  If  the  thermometers 
are  in  the  Fahrenheit  scale  it  is  more  convenient  to  have  the 
balance  weigh  in  pounds  and  hundredths  of  a  pound.  If  the  ther- 
mometers read  in  the  Centigrade  scale  it  is  more  convenient  to 
preserve  the  metric  unit  throughout.  The  water  should  be 
weighed  in  a  metal  bucket  or  glass  vessel  for  which  a  counter- 
poise is  provided.  It  is  convenient  to  counterpoise  the  bucket 
with  the  interior  wet  as  it  is  just  after  the  water  has  been  poured 
out  after  a  test.  Its  weight  will  be  so  nearly  constant  that  it  is 
not  necessary  to  counterpoise  after  each  test.  The  balance 
should  be  capable  of  carrying  ten  pounds  on  each  pan  with  a 
sensitiveness  of  one-hundredth  of  a  pound. 

8.  Description  of  Calorimeter. — The  illustrations  of  Fig.  22 
show  the  Junkers  calorimeter  which  has  served  as  the  model 
from  which  most  of  the  American  instruments  have  been  devel- 
oped. Some  of  the  American  instruments  embody  distinct  im- 
provements— such  as  ease  of  disassembly  for  repairs  or  cleaning, 
and  automatic  tipping  device  for  diverting  the  stream  of  heated 
water  from  the  measuring  bucket  when  the  meter  hand  has  made 
a  complete  revolution.  The  gas  coming  from  the  meter  is  burned 
in  a  Bunsen  burner  placed  in  the  cylindrical  combustion  chamber 
of  the  instrument.  The  hot  gases  rise  in  the  central  chamber, 
pass  down  through  a  series  of  small  tubes  in  the  annular  water 
jacket  surrounding  the  combustion  chamber,  unite  again  in  a 
single  flue  at  the  bottom  of  the  instrument  and  pass  out  through 
an  orifice  whose  size  may  be  regulated  by  a  damper.  Water 
enters  through  the  rubber  tube  w  to  the  small  elevated  tank  a 
which  serves  to  supply  water  to  the  calorimeter  under  a  constant 
head.  The  amount  of  water  flowing  into  the^nstrument  is  con- 
trolled by  the  valve  b  and  the  waste  water  from  a  is  discharged 
at  c.  The  water  traversing  the  instrument,  passes  out  at  d  and 
during  the  actual  test  is  measured  in  the  graduated  cylinder 
shown,  or  collected  in  a  vessel  and  subsequently  weighed. 

The  operation  of  the  instrument  is  shown  in  detail  in  Fig.  22. 
The  sectional  illustration  shows  the  burner  (2)  properly  placed 
in  the  combustion  chamber  (1)  and  the  path  of  the  combustion 
gases  and  the  water.  The  products  of  combustion  rise  in  the 


98 


GAS  AND  FUEL  ANALYSIS 


central  chamber,  turn  at  the  top,  descend  the  annular  cooling 
chamber  (3)  to  the  drum  (4),  pass  the  thermometer  (5)  and  es- 
cape at  (6).  The  water  rises  to  the  small  overflow  cup  (7)  tra- 
versing a  filter  of  wire  gauze.  The  excess  of  water  overflows  and 
passes  out  of  the  instrument  to  the  waste  pipe  through  a  rubber 


FIG.  22a.— Gas  calorimeter. 


FIG.  22b. — Section  of  gas  calorimeter. 


tube  attached  at  (8).  The  small  vessel  (7)  must  always  be  kept 
overflowing  to  insure  a  constant  pressure  and  hence  a  constant 
supply  of  water  through  the  valve  (9).  The  water  passes  the 
thermometer  (10)  which  registers  the  inlet  temperature,  descends 
in  a  small  pipe  within  the  outer  casing  to  the  bottom  of  the  instru- 


HEATING  VALUE  OF  GAS  99 

ment  and  rises  in  the  annular  chamber  surrounding  the  gas  pas- 
sages (3),  thus  passing  in  a  direction  opposite  to  that  of  the  com- 
bustion gases.  The  water  from  the  annular  chamber  passes 
through  the  drum  (11)  provided  with  baffle  plates  to  mix  it  and 
to  insure  that  all  parts  of  the  stream  are  of  uniform  temperature, 
passes  the  thermometer  (12)  which  registers  the  outlet  tempera- 
ture, to  the  overflow  vessel  (13)  and  out  at  (14). 

The  water  formed  in  the  combustion  of  the  hydrogen  and 
hydrocarbons  of  the  gas  is  condensed  as  it  descends  the  annular 
condenser  (3)  and  passes  out  of  the  drip  shown  at  e  of  Fig.  22a 
and  is  caught  in  a  graduated  cylinder.  The  working  parts  of  the 
calorimeter  thus  described  are  insulated  from  the  room  by  an 
air  jacket.  The  outer  casing  of  the  calorimeter  is  nickel-plated 
and  to  be  kept  polished  to  lessen  the  loss  of  heat  by  radiation. 
It  is  well  to  drain  the  calorimeter  when  not  in  use  by  opening  the 
cock  (16).  There  is  some  danger  that  air  brought  in  by  the  in- 
coming water  may  collect  around  the  inlet  thermometer  and 
disturb  the  accuracy  of  its  readings.  The  tube  (h)  shown  at  the 
top  of  the  calorimeter  in  Fig.  22a  is  to  allow  such  bubbles  to  escape. 
Any  water  entrained  by  the  bubbles  passes  out  of  the  small  over- 
flow. 

9.  Preliminaries  of  a  Test. — The  calorimeter  is  to  be  set  up 
on  a  table  where  the  light  is  good,  where  there  are  no  draughts, 
and  where  there  is  a  water  supply  and  a  waste  pipe.  Fig.  23 
shows  the  calorimeter  set  in  a  hood  which  has  been  modified  by 
lowering  a  portion  of  the  floor  to  bring  the  thermometer  more 
nearly  on  a  level  with  the  eye  of  the  observer.  On  the  top  of 
the  hood  is  a  zinc-lined  wooden  tank  connected  to  the  water 
supply  and  provided  with  an  overflow  pipe,  from  which  the 
water  supply  for  the  calorimeter  is  drawn.  This  large  overflow 
tank  is  necessary  to  compensate  for  variations  in  the  tempera- 
ture and  pressure  of  the  city  water  supply.  It  should  preferably 
hold  enough  water  for  the  day's  tests,  so  that  the  water  standing 
over  night  may  come  to  room  temperature. 

The  first  step  is  to  turn  on  the  water  and  regulate  the  supply 
so  that  it  flows  through  the  instrument  at  the  rate  of  approxi- 
mately 1.5  to  2.0  liters  per  minute  in  case  illuminating  gas  of 
ordinary  quality  is  to  be  tested.  The  water  must  continuously 
overflow  from  both  cups  (13)  and  (7)  of  Fig.  226.  No  water 


100 


GAS  AND  FUEL  ANALYSIS 


should  drip  from  spout  e  nor  from  any  other  part  of  the  instru- 
ment. 

The  gas  meter  is  to  be  levelled  and  water  added  if  necessary  to 
bring  the  bottom  of  the  meniscus  of  the  water  on  a  level  with  the 
pointer.  This  is  to  be  done  when  there  is  no  gas  pressure  on  the 
meter,  and  to  ensure  this  state  of  affairs  the  burner  cock  on 
the  outlet  of  the  meter  should  be  open  and  an  opening  should 
be  made  to  the  air  on  the  inlet  side  of  the  meter.  This  may 
usually  be  most  conveniently  effected  by  disconnecting  the  rub- 


FIG.  23. — Gas  calorimeter  and  accessories. 

ber  tube,  but  may  also  be  accomplished  by  unscrewing  the  small 
plug  at  the  bottom  of  the  well  below  the  gas  inlet.  This  also 
serves  the  purpose  of  removing  any  water  which  may  have 
spattered  into  the  gas  inlet.  The  probable  error  in  adjusting 
the  water  level  is  0.3  per  cent,  so  that  when  a  greater  accuracy 
is  required  the  meter  should  be  recalibrated  after  adjustment. 
The  gas  supply  is  to  be  connected  to  the  meter  and  then  to  the 
calorimeter.  A  pressure  regulator  is  unnecessary  on  a  city  gas 
supply  if  the  meter  works  smoothly.  Directions  are  frequently 


HEATING  VALUE  Off  G'AS  '  .  :  101 

given  to  interpose  a  regulator  of  the  floating  ;bfcli  -jar  type  .be- 
tween the  meter  and  the  calorimeter.  If  this  is  done  it  must 
be  watched  closely  because  any  variation  in  the  heights  of  the 
drum  of  the  regulator  at  the  beginning  and  end  of  the  test  causes 
an  error  in  the  measurement  of  the  gas.  Long  connections  of 
rubber  tubing  are  to  be  avoided  since  rubber  is  porous  and  also 
exerts  a  selective  solvent  action  on  the  hydrocarbons  of  the  gas. 
The  connections  should  be  of  glass  with  short  lengths  of  rubber 
on  each  end. 

The  system  is  to  be  tested  for  leaks  by  closing  the  burner  cock 
and  opening  the  inlet  cock  on  the  gas  main.  The  large  hand  of 
the  meter  should  not  show  any  perceptible  change  in  position 
after  two  minutes.  When  the  system  has  been  found  to  be  tight 
the  burner  cock  may  be  opened  and  the  gas  allowed  to  escape 
into  the  air  of  the  room  until  the  large  hand  of  the  meter  has  made 
one  complete  revolution.  It  may  then  be  lighted  without  danger 
of  explosion  unless  the  gas  is  acetylene,  uncarburetted  water  gas 
or  similar  gases  having  wide  explosive  limits.  Be  sure  that  no 
unburned  gas  gets  into  the  calorimeter  where  it  might  cause  ex- 
plosion later. 

The  flame  from  the  burner  is  to  be  regulated  so  that  it  is  a 
clear  blue  color  with  just  a  tinge  of  yellow  at  the  tip.  The 
volume  will  depend  on  the  quality  of  the  gas.  Special  tips  for 
gases  of  very  high  or  low  heating  value  are  provided  with  the 
instrument.  With  ordinary  illuminating  gas  the  rate  of  flow 
should  be  between  5  and  7  ft.  per  hour.  The  gas  should  be 
burned  with  a  small  excess  of  air.  The  draft  may  be  controlled 
by  the  butterfly  valve  (6)  of  Fig.  22.  The  valve  should  be  set 
to  give  maximum  readings  of  the  thermometer  on  the  water 
outlet.  That  setting  which  gives  the  highest  result  is  the  most 
accurate.  The  Burtau  of  Standards1  recommends  as  a  "  nor- 
mal rate,"  the  rate  of  70  per  cent,  of  the  maximum  attainable 
without  incomplete  combustion.  The  flame  must  burn  per- 
fectly steadily.  If  it  flickers  the  most  probable  cause  is  the 
presence  of  water  in  some  of  the  connections.  The  rubber  tub- 
ing should  be  disconnected  and  drained,  the  plug  in  the  well 
below  the  inlet  of  the  meter  removed,  and  the  pressure  regulator 
examined.  It  may  be  that  the  flickering  is  due  to  friction  within 

1  Technologic  Paper  No.  36. 


102  QA3  AND  FUEL  ANALYSIS 

the  meter  which  causes  the  drum  to  stick.  This  can  usually  be 
observed  by  closely  watching  the  large  hand  of  the  meter  and 
observing  if  it  lags  at  particular  points  of  its  revolution.  Trouble 
from  this  source  cannot  usually  be  remedied  without  sending  the 
meter  back  to  the  factory.  Flickering  of  the  flame  of  the  test 
burner  may  also  be  due  to  fluctuations  in  the  pressure  of  the  gas 
in  the  mains  or  services.  A  U-gage  attached  to  a  gas  outlet  will 
show  whether  this  is  the  case.  If  it  is  necessary  to  test  gas  under 
these  conditions  the  flickering  may  be  lessened  by  interposing 
between  the  gas  outlet  and  the  meter  a  large  empty  bottle.  Care 
must  be  taken  to  fill  this  bottle  completely  with  water  and  then 
displace  this  with  gas  to  avoid  danger  of  explosion. 

If  the  meter  has  been  recently  filled  with  fresh  water  the  gas 
should  be  allowed  to  burn  for  an  hour  before  the  test  in  order  that 
the  water  of  the  meter  may  become  saturated  and  not  cause  any 
change  in  the  composition  of  the  gas  passing  through  it. 

10.  Description  of  a  Test. — When  the  gas  and  water  supply 
and  the  burner  have  been  thus  adjusted,  the  lighted  burner  may 
be  placed  in  the  calorimeter,  care  being  taken  to  properly  center 
it  and  to  see  that  it  projects  far  enough  into  the  instrument  so 
that  the  top  of  the  burner  will  be  above  the  lower  level  of  the 
belt  of  cooling  water.  This  operation  is  facilitated  by  a  small 
mirror  placed  below  the  instrument.  The  thermometer  in  the 
outlet  water  will  at  once  commence  to  rise,  and  in  a  few  minutes 
will  be  constant  to  within  a  few  tenths  of  a  degree.  The  increase 
in  temperature  of  the  outflowing  over  the  incoming  water  should 
not  be  more  than  20°  F.  and  it  may  be  necessary  to  readjust  the 
water  and  gas  supply  to  obtain  this  condition.  If  it  is  necessary 
to  change  the  adjustment  of  the  gas  the  burner  should  be  removed 
from  the  calorimeter.  The  butterfly  valve  must  not  be  closed 
enough  to  prevent  the  flame  from  burning  strongly  and  freely. 
The  escaping  gases  should  not  have  any  odor  of  unburned  gas. 
Their  temperature  should  be  only  a  few  degrees  above  that  of  the 
water  entering. 

The  water  formed  in  the  combustion  of  the  hydrogen  and 
hydrocarbons  will  condense  in  the  calorimeter  and  commence 
to  drip  from  the  small  spout  at  the  bottom  of  the  instrument. 
The  test  should  not  be  commenced  until  the  thermometer  on  the 
water  outlet  has  remained  constant  for  several  minutes  and  the 


HEATING  VALUE  OF  GAS  103 

condensed  water  has  also  commenced  to  drip  from  its  spout 
showing  that  equilibrium  has  been  reached  within  the  calori- 
meter. 

The  counterpoised  bucket  for  the  water  is  placed  in  a  conve- 
nient position  and  as  the  large  hand  of  the  meter  passes  a  zero 
mark  the  water  is  turned  into  the  bucket.  Both  thermometers 
are  now  to  be  read  at  each  quarter  position  of  the  meter  hands  or 
more  frequently.  The  outlet  thermometer  sometimes  fluctuates 
rapidly  and  it  is  well  under  such  circumstances  to  read  it  as  many 
times  as  possible  so  as  to  obtain  a  fairer  average.  A  consumption 
of  0.2  of  a  cubic  foot,  or  two  revolutions  of  the  large  meter  hand  is 
sufficient  with  illuminating  gas.  The  last  thermometer  readings 
will  be  made  when  the  meter  hand  is  in  the  three-quarter  position. 
The  operator  then  watches  the  meter  while  holding  one  hand  on 
the  tube  through  which  the  outlet  water  is  flowing  and  as  the 
meter  hand  again  reaches  the  zero  he  swings  the  tube  out  of  the 
bucket,  thus  marking  the  completion  of  the  test.  After  the  water 
has  been  weighed  a  duplicate  test  may  at  once  be  started.  The 
procedure  is  the  same  in  case  the  water  is  to  be  measured  in  a 
graduated  cylinder  instead  of  being  weighed.  The  volume 
readings  of  the  cylinder  must  be  converted  into  grams  by  means 
of  the  table  in  §  6  of  Chapter  XVI  on  Manipulation  of  the  Bomb 
Calorimeter.  It  is  not  possible  to  read  the  volume  very  accu- 
rately in  a  wide  graduated  cylinder. 

The  water  of  condensation  dripping  from  the  instrument  is  to 
be  measured  to  allow  the  calculation  of  the  net  heating  value. 
It  is  accurate  enough  to  catch  the  water  formed  from  1  cu.  ft. 
in  a  50  c.c.  graduated  cylinder. 

In  case  the  temperature  readings  have  not  stayed  constant 
within  a  few  tenths  of  a  degree  during  the  test,  the  results  should 
be  discarded  and  an  attempt  be  made  to  better  the  conditions. 

If  for  any  reason  the  burner  goes  out  during  a  test  and  un- 
burned  gas  gets  into  the  instrument,  it  must  be  expelled  before 
again  lighting  the  flame.  This  may  readily  be  accomplished  by 
blowing  vigorously  through  the  escape  pipe  of  the  combustion 
gases. 

11.  Calculation  of  Observed  Heating  Value. — The  heating 
value  of  gas  is  usually  expressed,  in  English  speaking  countries, 
in  British  thermal  units  per  cubic  foot  of  gas  measured  when 


104  GAS  AND  FUEL  ANALYSIS 

saturated  with  moisture  at  60°  F.  and  under  a  barometric  pres- 
sure of  30  in.  of  mercury.  The  method  for  correcting  the  ob- 
served volume  of  gas  to  these  standard  conditions  has  been 
described  in  §  4.  The  factors  for  converting  cubic  centimeters 
of  water  at  various  temperatures  to  grams  are  given  in  §  6  of 
Chapter  XVI.  A  Calory  is  defined  accurately  enough  for  this 
work  as  the  amount  of  heat  required  to  heat  1  kg.  of  water  1°  C., 
and  a  British  thermal  unit  to  be  the  amount  required  to  heat  1  Ib. 
of  water  1°  F.  irrespective  of  the  temperature  of  the  water.  The 
formula  for  calculation  of  the  heating  value  is 


where  m  =  mass  of  water  heated 

t'  =  mean  temperature  of  water  flowing  out 
t  =  mean  temperature  of  water  flowing  in 
v  =  corrected  volume  of  gas  burned 

If  m  is  expressed  in  pounds,  t  in  degrees  Fahrenheit  and  v 
in  cubic  feet,  the  result  is  at  once  British  thermal  units  per  cubic 
foot. 

If  m  is  expressed  in  kilograms,  t  in  degrees  Centigrade  and  v 
in  cubic  feet,  the  result  is  in  the  hybrid  unit  Calories  per  cubic  foot 
which  may  be  corrected  to  British  thermal  units  per  cubic  foot  by 
multiplying  by  3.968. 

If  m  is  expressed  in  grams,  t  in  degrees  Centigrade  and  v  in 
liters  the  result  will  be  in  the  metric  unit,  small  calories  per  liter 
which  is  the  same  as  Calories  per  cubic  meter.  This  is  the 
method  of  reporting  heat  values  in  Germany  and  other  countries 
which  use  the  metric  system.  To  convert  Calories  per  meter 
to  British  thermal  units  per  cubic  foot  of  gas  measured  under 
the  same  condition  multiply  by  .1124.  In  scientific  work  the 
heating  value  of  a  gas  is  usually  reported  as  Calories  per  cubic 
meter  of  dry  gas  at  0°  C.  and  760  millimeters  pressure.  In  tech- 
nical work  in  Germany  the  gas  volumes  are  usually  corrected  to 
15°  C.  and  760  mm.  pressure  which  makes  the  conditions  prac- 
tically the  same  as  those  which  prevail  in  this  country. 

The  following  data  are  from  a  test  made  under  rather  unfa- 
vorable conditions  and  where  no  attempt  was  made  to  secure 


HEATING  VALUE  OF  GAS  105 

an  accuracy  closer  than  1  per  cent.  The  meter  used  passed 
0.1  cu.  ft.  of  gas  per  revolution,  the  thermometers  were  in  the 
Fahrenheit  scale  and  the  water  was  weighed  in  pounds. 

Meter  reading  at  start 21 . 200 

Meter  reading  at  close 21 . 400 

Meter  temperature 71°  F. 

Barometer 29 . 8 

Correction  factor  for  temperature  and  pressure 0 . 965 

Correction  factor  for  meter 0 . 996 

Temperature  of  water 

In  Out 

53.8°  70.9° 

53.9  70.8 

53.9  70.9 

53.8  70.9 

53.9  71.0 
53.9  70.9 
54.0  71.0 


Average  .....  53  .  88°  F.  ^          70.  91°  F. 

Calibration  correction  for  inlet  thermometer  .............    —0.1° 

Calibration  correction  for  outlet  thermometer  ............    +0.  1° 

Corrected  inlet  temperature  .....................    53  .  78°  F. 

Corrected  outlet  temperature  ....................    71  .  01°  F. 

Rise  in  temperature  of  water  ....................    17.  23°  F. 

Room  temperature  .............................    72°        F. 

Weight  of  water  heated  .........................      6  .  76  pounds 

Gas  burned,  corrected  0.2  X  0.965  X  0.996  =  0.192  cu.  ft. 
Uncorrected  heating  value  —  —  =  606  B.t.u. 


Correction  for  difference  in  temperature  be- 
tween inlet  water  and  room  temperature 
=-  0.7  B.t.u.  per  degree  F.  (see  Table 
VIII  of  Appendix) 

Temperature  inlet  water  ............   54°  F.  - 

Room  temperature  .................   72°  F. 

Difference  ........................    18°  F. 

Correction  to  be  subtracted  0.7  X  18      =  12  B.t.u. 

Observed  heating  value  594  B.t.u. 


106  GAS  AND  FUEL  ANALYSIS 

12.  Total  Heating  Value. — The  total  heating  value  of  a  gas 
has  been  denned  by  the  Bureau  of  Standards1  in  the  following 
terms.     "The  total  heating  value  of  a  gas,  expressed  in  the  Eng- 
lish system  of  units,  is  the  number  of  British  thermal  units  pro- 
duced by  the  combustion,  at  constant  pressure,  of  the  amount 
of  the  gas  which  would  occupy  a  volume  of  1  cubic  foot  at  a 
temperature  of  60°  F.,  if  saturated  with  water  vapor  and  under 
a  pressure  equivalent  to  that  of  30  inches  of  mercury  at  32°  F. 
and  under  standard  gravity,  with  air  of  the  same  temperature 
and  pressure  as  the  gas,  when  the  products  of  combustion  are 
cooled  to  the  initial  temperature  of  gas  and  air  and  the  water 
formed  by  combustion  is  condensed  to  the  liquid  state." 

It  is  believed  preferable  that  this  term  replace  the  term  "gross 
heating  value"  which  has  been  very  loosely  used.  The  total 
heating  value  differs  from  the  observed  heating  value  in  the 
application  of  certain  corrections  for  errors  which  while  minor 
may  cause  an  error  of  as  much  as  2  per  cent,  in  the  final  result. 
These  are  discussed  in  following  paragraphs. 

13.  Net  Heating  Value. — In  most  industrial  operations  the 
combustion  gases  are  not  cooled  to  room  temperature  before 
escaping  from  the  apparatus  and  therefore  some  of  the  heat  of 
the  gas  is  wasted.     This  is  due  to  a  lack  of  efficiency  of  the  appara- 
tus and  varies  with  individual  conditions.     There  are  so  many 
industrial  operations,  however,  where  the  water  formed  in  com- 
bustion escapes  as  steam  and  the  latent  heat  of  steam  formation 
is  so  large  when  compared  with  the  amount  of  heat  required  to 
raise  the  temperature  of  fixed  gases  or  of  water  or  steam  through 
moderate  temperature  intervals  that  the  value  of  the  latent  heat 
is  frequently  deducted  from  the  gross  heating  value.     The  re- 
sulting lower  value  is  called  the  net  heating  value. 

The  net  heating  value  is  defined  by  the  Bureau  of  Standards 
as  follows:-  "The  net  heating  value  of  a  gas,  expressed  in  the 
English  system  of  units,  is  the  number  of  British  thermal  units 
produced  by  the  combustion,  at  constant  pressure,  of  the  amount 
of  the  gas  which  would  occupy  a  volume  of  1  cubic  foot  at  a 
temperature  of  60°  F.,  if  saturated  with  water  vapor  and  under 
a  pressure  equivalent  to  that  of  30  inches  of  mercury  at  32°  F. 

1Waidner  and  Mueller,  Technologic  Paper  No.  36.  Industrial  Gas 
Calorimetry. 


HEATING  VALUE  OF  GAS  107 

and  under  standard  gravity,  with  air  of  the  same  temperature 
and  pressure  as  the  gas,  when  the  products  of  combustion  are 
cooled  to  the  initial  temperature  of  gas  and  air  and  the  water 
formed  in  combustion  remains  in  the  state  of  vapor.  According 
to  the  above  definitions  the  net  heating  value  is  less  than  the 
total  heating  value  by  an  amount  of  heat  equal  to  the  latent 
heat  of  vaporization,  at  the  initial  temperature  of  the  gas  and 
air,  of  the  water  formed  by  the  combustion  of  the  gas." 

The  heat  absorbed  when  one  gram  of  water  at  100°  C.  changes 
to  steam  at  the  same  temperature  is  0.536  Calories.  The  heat 
absorbed  in  the  change  of  liquid  water  at  10°  C.  to  vapor  at 
10°  C.  is  very  closely  0.600  Calories.  This  latter  figure  is  usu- 
ally employed  in  calculating  the  net  heating  value  which  is 
obtained  by  multiplying  the  number  of  cubic  centimeters  of 
condensed  water  dripping  from  the  calorimeter  during  the  com- 
bustion of  a  cubic  foot  of  gas  by  0.6,  and  3.968  to  convert  into 
British  thermal  units  and  then  subtracting  this  value  from  the 
observed  heating  value  in  British  thermal  units  per  cubic  foot. 
The  method  of  calculating  the  net  heating  value  in  the  test  re- 
ported in  the  preceding  section  is  as  follows: 


Meter  reading  at  start 21.200 

Meter  reading  at  close 22.100 

Gas  burned 0.900  cu.  ft.  uncorrected 

Gas  burned  corrected,  0.9X0.965X0.996=0.86  cu.  ft. 
Condensed  water  collected,  21.8  c.c. 

21  8 
Condensed  water  formed  per  cu.  ft.  gas?T      =25.4  c.c. 


Latent  heat  of  condensed  water  25.4X0.6X3.968=60  B.t.u. 

Uncorrected  heating  value  of  gas 606  B.t.u. 

Correction  for  difference  in  temperature  between 

inlet  water  and  room  temperature  =0.4  B.t.u.  per 

degree  F.  (see  Table  VIII  of  Appendix). 

Corrections  to  be  subtracted  0.4X18=  7 

Latent  heat  of  condensed  water 60     67 

Net  heating  value  of  gas 539  B.t.u. 

14.  Calculation  of  Total  Heating  Value. — The  calculation  of 
Observed  Heating  Value  given  in  Section  11  must  be  modified 


108  GAS  AND  FUEL  ANALYSIS 

by  taking  account  of  the  following  errors  in  order  to  calculate 
Total  Heating  Value. 

Temperature  correction  for  barometer. 

Correction  for  pressure  of  gas  at  meter. 

Correction  for  emergent  stem  of  thermometer. 

Correction  for  variation  in  temperature  of  inlet  water. 

Correction  for  variation  in  temperature  of  escaping  gases.  \; 

Correction  for  humidity  of  air.   - 

Correction  for  humidity  of  gas. 

An  illustration  of  a  complete  record  and  calculation  with  cor- 
rection for  all  errors  as  taken  from  Circular  48  of  the  Bureau  of 
Standards  forms  is  given  in  Fig.  24. 

15.  Accuracy  of  Method. — The  accuracy  of  gas  calorimeters 
has  been  thoroughly  investigated  by  the  Committee  on  Calori- 
metry1  of  the  American  Gas  Institute  and  subsequently  by  the 
Bureau  of  Standards.2  Both  investigations  agree  that  continu- 
ous flow  calorimeters  give  substantially  accurate  results  when 
properly  constructed  and  operated. 

The  sources  of  error  are  as  follows: 

Errors  in  Registration  of  Gas  Volume. — If  the  meter  is  in  good 
condition  and  is  calibrated  after  the  water  level  has  been  ad- 
justed the  error  of  the  meter  need  not  exceed  one-tenth  of  1  per 
cent.  If  these  precautions  are  neglected  the  error  may  be  large. 
The  error  of  observation  will  be  about  one  small  division  of  the 
large  scale  corresponding  to  1  part  in  200  or  0.5  per  cent,  error 
in  a  test  as  ordinarily  run. 

Errors  in  Measurement  of  Temperature. — If  the  thermometers 
are  accurately  calibrated,  the  water  supply  of  constant  tempera- 
ture and  the  consumption  of  gas  and  its  heat  value  constant  dur- 
ing a  test,  there  should  be  practically  no  instrumental  error.  If 
the  constancy  of  any  of  these  conditions  is  upset  there  will  be 
errors  due  partly  to  lag  in  the  thermometers  which  do  not  in- 
stantly respond  to  the  changed  condition.  An  error  which  is 
negligible  except  in  the  most  accurate  work  is  that  caused  by  the 
different  temperature  of  the  bulb  and  the  stem  of  the  thermom- 
eter. There  will  be  no  correction  for  the  emergent  stem  of  the 

lProc.  Am.  Gas  Inst.,  1908,  285;  1909,  148;  1912,  65. 

2  Technologic  Paper  No.  36.     Industr.il1  Gas  Calorimetry,  1914. 


HEATING  VALUE  OF  GAS 


109 


HEATING  VALUE  TEST  RECORD 

Place      /^LLf/TJJIJJs  Jg£&4 .        Date._(fM,J?^A2v..     Time  __/<?_&..? 
Calorimeter  No_iZ"/.-?i.?.£    Meter  No_^?_?_/_4._.  Thermometer  No..     In 

Gas  liuepurgtd£°°  Meter  adjusted ]£    Leak»e»t|£     Water  valve____4.C 

Diffenential  therm. corr'n  det'd-- v2c£-/x/-/^?-(date).      Last  meter  calibration.  J 


BTAKT 

E»D 

SERIES  No.l 

BEK1ES  No^ 

BEKfES  NoJ 

later 

Ob-ILET 

I.NLET 

OfTLCT 

INLIT 

OtTLIT 

Temp.of  barometer    

6,8° 

^>8  " 

Preliminary 

&77# 

9t>S</- 

(,J.J3 

p&.y-o 

67-70 

8&40 

2  <JS  2 

3.1SI 

SO 

U-f" 

H-5 

Certif.  corr'n    _ 

-.a/ 

50 

h,Q 

1-8 

-./o 

//3 

H.Q 

40 

Corr'd.barom.  height      

2.9.&0 

3d 

h,  7 

39 

Pressure  at  meter 
(Inches  in  water) 

Equlv.  (  inches  of  mercury  ) 
Total  gas  pressure    

AJ"| 

4-3 

V7 

Q-3 

.// 

5"V 

So 

JlQ 

3-frS/ 

Used  in 

67/3 

1-9 

t>7-j3 

S"o 

t>7-fO 

S2 

Meter  therm,  reading  
Certif.  corr'n  

(*~8.i  |6<?.3 

areragmg. 

SO 

[L  1 

So 

".3 

So 

V-o 

VO 

&  73 

v-7 

i/.g 

42 

Reduction  factor  F    

0.963 

y-o 

39 

f_5 

*       ,                 (  wet  bulb 

53.0 

SW 

Psjchrometer   J 
'    dry  bulb 

6,3.0 

6&S~ 

Humidity 

2>5oft 

lj.q 

m 

^6 

()  J 

Bupplementary 

6"7?J 

36 

t>7-?2 

if,/ 

bJ'fO 

£2 

Time  of  1  meter  rev.  
Equlv.  rat«(eu.ft.per  hr.) 

SzL' 

Average                       

\y~/'/*3 

(>793 

?6.^--5 

(aj.90 

fftii-S 

6>-9 

CertifioaU  corr'n   ._    _ 

-.2.8 

-2S 

] 

CONDENSED  WATEK 

MeUr  reading:  start    
•>      «nd 

COLLECT 

:D 

Differential  corr'n   ._    . 

-02 

\-IS 

—  /? 

~/g 

-/? 

18.1 

Emergent  stem  corr'n 

i-08 

) 

/?./ 

2  O.<4- 

Certificated  temp.  

&77S 

8^.2-7 

6775 

ff6.2.6 

Condensate(oc)    

±/.6 

2-1.2. 

Temp,  rise  T 

/g.S~2. 

IS.5  1 

ISSLf 

••       percu.ft,(00°801n.) 

12.-3 

2-I.J 

Water  heated  W  

6./£- 

6.7  4- 

(0.12. 

Average  A  _  _         _ 

3-2..I 

No.  of  rev.  of  meter  
Meter  eallb.  1  rev.  =  

2. 

NET  HEATING  VALUE 

O  .  look 

Observed  heating  value  average     _.     O  *f-  U~ 

Gas  volume  V  

0.2.0/2. 

.  -h      1 

Obnrved  beating  rake 
WX    T 

£¥f 

&l^ 

C^3 

Keductlon  te  netfA  X  2.9)  —  JT  / 

Net  heating  value 

.  $?  V- 

Corr'n  for  heat  loss  .._ 

•/•  / 

Certified  as  correct. 

££3&. 

Corr'n  for  atmoe.bnmid. 

•/•  ^ 

Total  heating  value. 

&  4-  <? 

G  4-7  * 

(*  l±& 

Obtirvtr. 

Average  

&  tf.  t?              Btu.  per  cu.ft.(6C°  8P  In.) 

FIG.  24. — Complete  record  sheet  for  determination  of  heating  value  of  gas: 
from  Circular  48,  Bureau  of  Standards. 


110  GAS  AND  FUEL  ANALYSIS 

inlet  thermometer  if  the  inlet  water  is  at  room  temperature.  If 
the  room  temperature  is  70°  F.,  and  the  temperature  of  the  out- 
let water  is  90°  F.,  an  addition  of  from  0.07  to  0.10°  F.,  should 
be  made  to  the  observed  reading  of  the  outlet  thermometer,  the 
exact  amount  depending  on  the  depth  to  which  the  stem  of  the 
thermometer  is  immersed  in  the  water.  Detailed  tables  of  these 
corrections  form  Table  VII  of  the  Appendix  of  this  book.  A 
more  important  error  due  to  changed  conditions  during  a  test 
results  from  the  large  volume  of  water  always  contained  in  the 
calorimeter. 

A  calorimeter  may  contain  approximately  four  pounds  of  water 
so  that  a  test  may  be  half  completed  before  any  of  the  water 
whose  temperature  has  been  taken  at  the  inlet,  reaches  the  out- 
let. In  case  the  temperature  of  the  inlet  water  shows  any  con- 
siderable variation  it  is  wiser  not  to  stop  the  readings  with  the 
termination  of  the  test  but  continue  to  read  the  outlet  thermom- 
eter at  the  regular  intervals  for  a  third  revolution  of  the  meter 
hand,  and  to  use  the  inlet  temperatures  of  the  first  and  second 
revolutions  and  the  outlet  temperatures  of  the  second  and  third 
revolutions,  in  making  the  computations.  It  will  be  evident 
that  the  larger  the  volume  of  water  in  the  calorimeter  the  greater 
is  the  possible  error  from  this  source.  The  error  in  making  a 
single  reading  of  the  thermometers  should  be  less  than  a  tenth 
of  a  degree  and  the  mean  error  of  a  series  of  seven  observations 
should  not  be  over  0.05°.  On  a  rise  of  ten  degrees  this  corre- 
sponds to  0.5  per  cent.  This  average  of  seven  readings  will  not 
give  the  correct  mean  temperature  of  the  water  unless  the  in- 
dividual readings  differ  from  each  other  only  by  a  few  tenths  of  a 
degree. 

Errors  in  Determination  of  Mass  of  Water  Heated. — The  error 
in  weighing  the  water  should  be  less  than  0.1  per  cent,  but  an 
error  of  a  second  in  terminating  the  experiment  means  a  possible 
0.8  per  cent.  This  is  a  greater  time  error  than  necessary  but 
the  probable  error  in  this  process  will  be  0.5  per  cent. 

Error  Due  to  Incomplete  Combustion. — When  the  calorimeter  is 
properly  adjusted,  this  error  should  vanish. 

Errors  Due  to  Sensible  Heat  and  Uncondensed  Water  Vapor 
Escaping  in  Combustion  Gases. — As  the  gases  pass  down  through 
the  calorimeter  they  meet  water  of  progressively  lower  tempera- 


HEATING  VALUE  OF  GAS 


111 


ture  until  just  before  leaving  the  calorimeter  they  are  surrounded 
by  water  of  the  temperature  recorded  by  the  inlet  thermometer. 
They  should  therefore  leave  the  instrument  at  a  temperature 
within  a  few  degrees  of  that  of  the  inflowing  water.  With  a 
theoretical  air  supply  the  error  from  this  loss  of  sensible  heat  in 
the  dry  gas  is  less  than  0.3  B.t.u.  per  degree  of  temperature 
difference  per  cubic  foot  of  gas  burned.  According  to  the  report 
made  to  the  American  Gas  Institute,1  the  actual  errors  observed 
as  due  to  this  source  were  only  0.5  B.t.u.  per  degree  per  cubic 
foot  even  when  the  temperature  of  the  inlet  water  was  far  from 
that  of  the  room.  The  actual  figures  recalculated  slightly  are 
given  below. 


Temp, 
inlet 
water 

Temp, 
exhaust 
gases 

Difference  between 
temp,  exhaust  gas 
and  inlet  water 

Error  in  heat  value 
due  to  sensible  heat 
of  dry  gases  of  com- 
bustion, B.t.u. 

Error  per 
degree 
difference 

Deg.  F. 

39 

45.6 

+6.6 

+3.7 

0.56 

49 

54.2 

+5.2 

+2.V 

0.52 

59.6 

63.2 

+3.6 

+  1.8 

0.50 

70.4 

72.4 

+2.0 

+  1.0 

0.50 

80.5 

81.5 

+  1.2 

+0.3 

0.23 

89.3 

88.6 

-0.7 

-0.5 

0.70 

The  error  due  to  water  vapor  in  the  exhaust  gases  may  be 
more  serious.  The  exhaust  gases  always  leave  the  calorimeter 
saturated  with  water.  The  gas  burned  having  passed  through  a 
wet  meter  is  also  practically  saturated  with  water.  The  air  for 
combustion,  whose  theoretical  volume  for  illuminating  gas  is 
roughly  six  times  the  volume  of  the  gas,  and  whose  actual  volume 
may  be  twice  that,  is  drawn  from  the  room  and  may  vary  widely 
in  humidity.  The  maximum  error  which  can  thus  be  introduced 
may  be  indicated  by  the  following  calculation.  It  is  assumed 
that  one  volume  of  gas  is  burned  with  six  volumes  of  air  and  that 
the  volume  after  combustion  contracts  to  six  volumes.  The 
water  formed  in  combustion  will  remain  in  the  vapor  form  so  far 
as  the  gases  can  hold  it  and  the  remainder  will  condense  in  the 


Proc.  Am.  Gas  InsL,  1909,  168. 


112  GAS  AND  FUEL  ANALYSIS 

calorimeter.  The  one  volume  of  gas  burned  entered  the  calor- 
imeter saturated  with  water  so  that  only  additional  water  to 
saturate  5  cu.  ft.  need  come  from  combustion.  The  weight  of 
water  vapor  per  cubic  foot  of  gas  will  vary  with  the  temperature 
as  shown  in  the  following  table. 

Wt.  vapor  in 
Temp.  mixed  cu.  ft. 

gas  and  vapor 

32°  F 0.000304  Ib. 

42°  F 0.000440  Ib. 

52°  F 0.000827  Ib. 

62°  F 0.000881  Ib. 

72°  F 0.001221  Ib. 

82°  F 0.001667  Ib. 

92°  F 0.002250  Ib. 

The  following  examples  will  serve  as  an  illustration  of  the  use 
of  these  figures. 

(1)  Assume  that  the  air  enters  at  62°  and  50  per  cent,  saturated 
with  water  vapor,  the  gas  enters  at  62°  saturated  with  moisture 
and  the  exhaust  gases  escape  at  82°. 

Moisture  brought  in  6  cu.  ft.  air  at    0.00044=0.00264  Ib. 
Moisture  brought  in  1  cu.  ft.  gas  at    0 . 00088  =  0 . 00088  Ib. 

(UX)3~52~ 

Moisture  carried  out  by  6  cu.  ft.  gas  at  0.00166  0 . 01000 
Excess   of   moisture   supplied   from    water   of 

combustion  0 . 00648  Ib. 

Latent  heat  =  1070  B.t.u.  per  Ib. 
Heat  lost  =0.00648X1070  =  6.9  B.t.u. 

This  is  an  unusually  large  error  since  there  is  no  need  of  letting 
the  exhaust  gases  escape  at  such  a  high  temperature.  If  they 
had  escaped  at  72°  the  error  from  this  source  would  have  been 
only  4.1  B.t.u.  If  they  had  escaped  at  62°  the  error  would  have 
been  only  1.9  B.t.u.  If  they  had  escaped  at  52°  or  10°  below 
room  temperatures  the  error  would  have  been  almost  zero. 

This  error  is  present  in  almost  all  operations  but  when  care  is 
taken  to  have  the  temperature  of  the  exhaust  gases  a  few  degrees 
below  that  of  the  room  the  error  should  not  be  over  3  B.t.u. 
It  will  usually  make  the  result  too  low  but  in  cases  where  the  room 


HEATING  VALUE  OF  GAS 


113 


is  warm  and  the  air  nearly  saturated  with  water  it 
may  be  in  the  other  direction. 

The  most  accurate  results  are  obtained  by 
keeping  the  temperature  of  the  gas  and  the  ex- 
haust at  room  temperature  and  correcting  for  the 
humidity  of  the  air  according  to  Table  V  of  the  > 
Appendix  when  gas  of  approximately  600  B.t.u.  is 
being  tested  and  according  to  Table  VI  when 
natural  gas  of  about  1000  B.t.u.  is  being  heated. 
Under  these  conditions  the  error  will  be  about 
1  B.t.u.  Before  using  this  table  the  humidity  of 
the  air  must  be  determined  as  directed  in  the 
following  Section.  The  corrections  are  expressed 
in  B.t.u.'s  and  are  to  be  added  where  the  sign  is 
+  and  subtracted  where  it  is  — . 

Loss  of  Heat  by  Radiation. — The  calorimeter  is 
protected  against  interchange  of  heat  with  the 
outside  air  by  an  insulating  air  chamber  enclosed 
in  a  polished  metal  jacket.  The  efficiency  of  this 
protection  is  given  in  the  report  of  the  Committee 
on  Calorimetry  of  the  American  Gas  Institute  for 
1908  as  99.5  per  cent.  The  metal  jacket  should 
be  kept  bright  in  order  to  maintain  this  efficiency. 

Accuracy  of  the  Process  as  a  Whole. — None  of  the 
various  preceding  sources  of  error  need  amount  to 
over  0.5  per  cent.  They  will  partially  offset  one 
another.  When  great  care  is  taken  the  total  error 
may  not  be  over  1  per  cent.  Under  ordinary  con- 
ditions it  is  not  safe  to  assume  that  the  error  will  be 
less  than  2  per  cent. 

16.  Determination  of  Humidity  of  Air. — The  fol- 
lowing directions  for  the  measurement  of  atmos- 
pheric moisture  are  given  by  the  U.  S.  Weather 
Bureau.1  The  most  reliable  instrument  for  this 

purpose  is  the  sling,  or  whirled  psychrometer.     In       pIG    25. 

special  cases  rotary  fans,  or  other  means,  may  be    Sling    psy- 
employed  to  move  the  air  rapidly  over  the  thermo-    chrometer. 
meter  bulbs.     In  any  case  satisfactory  results  can- 

1  U.  S.  Dept.  Agriculture,  W.  B.  No.  235,  Psychrometric  Tables. 


I 

al 


114  GAS  AND  FUEL  ANALYSIS 

not  be  obtained  from  observations  in  relatively  stagnant  air. 
A  strong  ventilation  is  absolutely  necessary  to  accuracy. 

The  sling  psychrometer  consists  of  a  pair  of  thermometers, 
provided  with  a  handle  as  shown  in  Fig.  25,  which  permits  the 
thermometers  to  be  whirled  rapidly,  the  bulbs  being  thereby 
strongly  affected  by  the  temperature  of  and  moisture  in  the  air. 
The  bulb  of  the  lower  of  the  two  thermometers  is  covered  with 
thin  muslin,  which  is  wet  at  the  time  an  observation  is  made. 

It  is  important  that  the  muslin  covering  for  the  wet  bulb  be 
kept  in  good  condition.  The  evaporation  of  the  water  from  the 
muslin  always  leaves  in  its  meshes  a  small  quantity  of  solid 
material,  which  sooner  or  later  somewhat  stiffens  the  muslin  so 
that  it  does  not  readily  take  up  water.  This  will  be  the  case  if 
the  muslin  does  not  readily  become  wet  after  being  dipped  in 
water.  On  this  account  it  is  desirable  to  use  as  pure  water  as 
possible,  and  also  to  renew  the  muslin  from  time  to  time  New 
muslin  should  always  be  washed  to  remove  sizing,  etc.,  before 
being  used.  A  small  rectangular  piece  wide  enough  to  go  about 
one  and  one-third  times  around  the  bulb,  and  long  enough  to 
cover  the  bulb  and  that  part  of  the  stem  below  the  metal  back, 
is  cut  out,  thoroughly  wetted  in  clean  water,  and  neatly  fitted 
around  the  thermometer.  It  is  tied  first  around  the  bulb  at  the 
top,  using  a  moderately  strong  thread.  A  loop  of  thread  to  form 
a  knot  is  next  placed  around  the  bottom  of  the  bulb,  just  where 
it  begins  to  round  off.  As  this  knot  is  drawn  tighter  and  tighter 
the  thread  slips  off  the  rounded  end  of  the  bulb  and  neatly 
stretches  the  muslin  covering  with  it,  at  the  same  time  securing 
the  latter  at  the  bottom. 

To  make  an  observation,  the  so-called  wet  bulb  is  thoroughly 
saturated  with  water  by  dipping  it  into  a  small  cup  or  wide- 
mouthed  bottle.  The  thermometers  are  then  whirled  rapidly 
for  fifteen  or  twenty  seconds;  stopped  and  quickly  read,  the  wet 
bulb  first.  This  reading  is  kept  in  mind,  the  psychrometer  im- 
mediately whirled  again  and  a  second  reading  taken.  This  is  re- 
peated three  or  four  times,  or  more,  if  necessary,  until  at  least 
two  successive  readings  of  the  wet  bulb  are  found  to  agree  very 
closely,  thereby  showing  that  it  has  reached  its  lowest  tempera- 
ture. A  minute  or  more  is  generally  required  to  secure  the  cor- 
rect temperature.  In  whirling  and  stopping  the  psychrometer 


HEATING  VALUE  OF  GAS  115 

the  arm  is  held  with  the  forearm  about  horizontal,  and  the  hand 
well  in  front.  A  peculiar  swing  starts  the  thermometers  whirling, 
and  afterward  the  motion  is  kept  up  by  only  a  slight  but  very 
regular  action  of  the  wrist,  in  harmony  with  the  whirling  ther- 
mometers. The  rate  should  be  a  natural  one,  so  as  to  be  easily 
and  regularly  maintained.  If  too  fast,  or  irregular,  the  ther- 
mometers may  be  jerked  about  in  a  violent  and  dangerous  man- 
ner. The  stopping  of  the  psychrometer,  even  at  the  very  highest 
rates,  can  be  perfectly  accomplished  in  a  single  revolution,  when 
one  has  learned  the  knack.  This  is  only  acquired  by  practice, 
and  consists  of  a  quick  swing  of  the  forearm  by  which  the  hand 
also  describes  a  circular  path,  and,  as  it  were,  follows  after  the 
thermometers  in  a  peculiar  manner  that  wholly  overcomes  their 
circular  motion  without  the  slightest  shock  or  jerk.  The  ther- 
mometers may,  without  very  great  danger,  be  allowed  simply  to 
stop  themselves;  the  final  motion  in  such  a  case  will  generally  be 
quite  jerky,  but,  unless  the  instrument  is  allowed  to  fall  on  the 
arm,  or  strikes  some  object,  no  injury  should  result. 

The  tables  from  which  humidity  may  be  calculated  form 
Table  IV  of  the  Appendix  and  give  the  data  for  a  barometric 
pressure  of  29.0  inches  of  mercury.  Their  use  is  illustrated  by 
the  following  example. 

Air  temperature  t  =75.0°  F. 

Wet  bulb  reading  t'  =  66.0°  F. 

t-t'      =  9.0°  F. 

In  table  opposite  75°  in  column  9.0  is  found  63. 
Relative  humidity  =  63  per  cent. 


If  the  barometric  pressure  had  not  been  29  in.  a  slight  error 
would  have  been  introduced  whose  magnitude  may  be  judged 
from  the  following  examples  of  the  same  problem  at  different 
barometric  pressures. 

Barometric  pressure  30  Relative  humidity  63 

Barometric  pressure  27  Relative  humidity  63 

Barometric  pressure  25  Relative  humidity  64 


116  GAS  AND  FUEL  ANALYSIS 

The  Weather  Bureau  report  235  referred  to  above  gives  fuller 
tables  and  may  be  obtained  from  the  Bureau  for  10  cents. 

17.  Non-continuous  Water  Heating  Calorimeters. — In  the 
third  edition  of  his  Gas  Analysis,  Hempel  described  a  calorimeter 
where  a  volume  of  about  a.  liter  of  gas  was  measured  in  a  glass 
cylinder,  passed  through  a  small  burner  and  burned  in  a  stream 
of  oxygen  within  a  calorimeter  containing  a  known  mass  of  water. 
The  rise  in  temperature  of  the  water  gave  the  data  for  the  calcu- 
lation of  heat  value,  after  the  instrument  had  been  calibrated  by 
the  combustion  of  hydrogen. 

The  Graefe  calorimeter  is  a  commercial  instrument  of  the  same 
general  type  but  somewhat  larger.  The  instrument  is  rather 
crudely  constructed  and  allows  the  exhaust  gases  to  escape  at 
an  unduly  high  temperature  so  that  it  is  necessary  to  calibrate 
it  against  some  standard  calorimeter.  An  inherent  defect  in 
calorimeters  of  this  type  comes  from  the  increasing  temperature 
of  the  exhaust  gases  as  the  test  proceeds  and  the  water  of  the 
calorimeter  becomes  warmer. 

The  Parr1  calorimeter  aims  to  compensate  for  this  error  and 
errors  due  to  moisture  in  the  exhaust  gases  by  providing  two  du- 
plicate calorimeters,  one  of  which  runs  on  pure  hydrogen  while 
the  other  is  testing  the  unknown  gas.  The  variation  from  the 
correct  result  shown  by  the  hydrogen  calorimeter  is  taken  as  the 
correction  to  be  applied  to  the  other  result.  The  Committee  on 
Calorimetry  of  the  American  Gas  Institute  in  its  1912  report 
states  that  this  calorimeter  if  properly  operated  gives  correct 
results  but  that  it  is  rather  complicated  in  construction,  and 
requires  more  skill  for  its  proper  operation  than  the  other  types. 
The  instrument  gives  total  heating  values  only. 

The  Doherty  calorimeter  is  a  compact  instrument  which  meas- 
ures the  gas  in  an  annular  cylinder  surrounding  the  combustion 
chamber  and  its  water  jacket.  The  gas  is  displaced  by  the 
warmed  water  which  has  flowed  through  this  water  jacket  or  heat 
absorption  chamber,  and  thermometer  readings  are  taken  as  the 
water  level  passes  fixed  points  on  the  gage  glass.  No  meter  is 
required  and  the  water  is  neither  weighed  nor  measured.  The 
Committee  on  Calorimetry  of  the  American  Gas  Institute  in 

1  J.  Ind.  and  Eng.  Chem.,  2,  337  (1910). 


HEATING  VALUE  OF  GAS  117 

its  1912  report  states  that  this  calorimeter  when  operated  prop- 
erly gives  the  same  efficiency  as  the  Junkers  calorimeter. 

18.  Automatic  and  Recording  Gas  Calorimeters. — The  form- 
ula for  the  calculation  of  the  heating  value  of  a  gas  as  given  in 

§  11  of  this  chapter  is  E.V.«— -.     It  is  evident  that  if 

the  ratio  —  can  be  kept  a  constant  and  t  can  also  be  kept  con- 
stant that  the  heating  value  can  be  readily  determined  from  a 
single  reading  of  t'  or  can  be  continuously  determined  by  a  re- 
cording thermometer  showing  the  temperatures  of  the  outlet 

water.     In  the  Junkers  continuous  calorimeter  the  ratio  —  is 

kept  constant  by  passing  both  gas  and  inlet  water  through  meters 
whose  drums  are  geared  together  by  a  chain  forcing  them  to 
rotate  always  proportionately.  There  are  various  other  types  of 
automatic  calorimeters.  In  every  case  they  should  be  checked 
occasionally  by  a  direct  determination  with  a  standard  instru- 
ment. 

19.  Calculation  of  Heating  Value  from  Chemical  Composi- 
tion.— If    the    heating    value    and    the    proportion    of    each 
constituent  in  a  mixed  gas  is  accurately  known,  it  is  possible 
to  calculate  the  heating  value  of  the  mixture.    Table  IX  gives 
the  heating  value  as  well  as  other  properties  of  a  number  of 
gases. 

If  each  constituent  in  the  gas  were  known,  the  heating  value 
calculated  from  this  data  would  probably  give  accurate  results. 
However,  when  it  is  noted  that  among  the  defines,  propylene 
has  a  heating  value  approximately  50  per  cent,  greater  than  ethy- 
lene,  and  butylene  a  heating  value  almost  double  that  of  ethylene 
it  will  be  seen  that  there  is  dangerous  latitude  for  arbitrary 
assumptions  as  to  the  constituents  of  the  olefines.  When  the 
"  illuminants  "  as  reported  include  not  only  the  olefines  but  ben- 
zene the  error  involved  in  an  arbitrary  assumption  of  the  mean 
heating  value  becomes  still  greater.  The  varying  members  of 
the  methane  series  also  possess  widely  differing  heating  values. 
Earnshaw1  gives  an  analytical  method  for  determining  the  mean 
composition  of  the  olefines  and  for  differentiating  between  me- 

1  Jour.  Franklin  Inst.,  146,  161  (1898). 


118  GAS  AND  FUEL  ANALYSIS 

thane  and  ethane.  The  method  is,  however,  difficult  analytically, 
and  the  results  when  obtained  are  not  entitled  to  the  degree  of 
confidence  which  pertains  to  those  obtained  directly  in  a  calori- 
meter. 

The  probable  error  involved  in  this  method  of  calculating  the 
heating  value  of  gas  (unless  Earnshaw's  complex  analysis  is 
followed  out)  is  about  5  per  cent.  In  the  case  of  carburetted 
water  gas  it  is  still  higher.  In  the  case  of  producer  gas  where  the 
total  percentage  of  hydrocarbon  is  low  and  where  all  suspended 
tar  particles  have  been  removed  the  results  are  more  accurate,. 


CHAPTER  VIII 
CANDLE  POWER  OF  ILLUMINATING  GAS 

1.  Introduction. — The  use  of  candle  power  as  a  standard  test 
of  illuminating  gas  was  practically  universal  before  1900.  The 
most  efficient  of  the  early  types  of  gas  burner  was  the  Argand  and 
quite  naturally  it  was  used  as  the  test  burner.  When  carburetted 
water  gas  of  high  candle  power  came  into  use  a  bats-wing  burner 
was  found  to  be  more  efficient  and  was  in  some,  cases  allowed. 
The  Welsbach  mantle  was  developed  later  and  its  efficiency  was 
found  to  be  more  nearly  in  proportion  to  the  heating  value  of  the 
gas  than  to  its  candle  power.  The  proportion  of  gas  burned  in 
luminous  flames  is  now  so  small  in  proportion  to  that  burned  for 
development  of  heat  that  tests  of  candle  power  have  become  of 
minor  importance  and  are  in  a  fair  way  to  become  obsolete  as  a 
criterion  of  quality  of  gas.  Photometry  deals  with  the  measure- 
ment of  the  intensity  of  light.  The  term  light  as  used  here  in- 
cludes only  those  rays  which  excite  vision  in  the  human  eye, 
which  thus  necessarily  becomes  the  final  arbiter  in  photometric 
tests.  The  eye  cannot  estimate  absolutely  the  amount  of  light 
which  stimulates  it.  It  can  compare  roughly  the  intensity  of 
illumination  from  two  sources  and  it  can  determine  with  more 
precision  when  the  intensities  from  two  sources  are  the  same. 
In  the  sense  in  which  it  is  here  used,  photometry  consists  in  the 
comparison  of  two  lights,  one  of  which  is  .a  standard.  The 
photometer  is  a  device  which  assists  the  eye  in  determining  when 
the  two  lights  are  of  the  same  intensity.  The  intensity  of  light 
entering  the  photometer  is  changed  by  varying  the  distance 
between  the  photometer  and  the  light,  the  intensity  of  light  from 
a  given  source  varying  inversely  as  the  square  of  the  distance. 
When  the  adjustments  have  been  made  so  that  the  intensity  of 
light  impinging  on  the  photometer  from  the  two  sources  is  the 
same,  as  shown  by  the  equal  illumination  of  the  two  photometer 
faces,  the  ratio  of  the  unknown  light  to  the  standard  light  be- 
comes mathematically  calculable  from  the  relative  distances  of 
the  lights  from  the  point  of  equal  illumination.  The  value  of 

119 


120  GAS  AND  FUEL  ANALYSIS 

luminous  intensity  is  in  English-speaking  countries  and  in  France 
expressed  in  candle-power. 

2.  Method  of  Rating  Candle-power. — The  light  emitted  from 
a  single  incandescent  particle  would  illuminate  uniformly  every 
point  of  an  enveloping  sphere  and  the  intensity  of  illumination 
might  be  measured  equally  well  at  any  point  on  the  sphere. 
When  the  light  to  be  measured  comes  from  a  surface  of  finite  size 
as  is  always  the  case  in  practice,  there  is  interference  with  the  free 
path  of  the  light  waves  from  a  single  particle  in  one  or  more  direc- 
tions so  that  the  illumination  of  the  enveloping  sphere  is  no  longer 
uniform.     It  is  possible  by  the  use  of  reflecting  mirrors  to  deter- 
mine the  illumination  at  various  points  on  the  circumference  of  a 
polar  circle  and  to  plot  from  this  data  a  curve  showing  the  dis- 
tribution of  light  at  various  angles.     Methods  of  this  sort  are 
often  resorted  to  in  a  study  of  illumination  where  it  is  desired  to 
determine  the  value  of  a  light  source  for  a  particular  purpose. 
This  method  is,  however,  rarely  followed  where  it  is  simply  a 
question  of  testing  the  quality  of  the  gas.     The  simpler  custom  of. 
taking  the  horizontal  candle-power  given  by  a  conventionalized 
burner  under  conventional  conditions  as  indicating  the  value  of 
the  gas,  has  become  well  established. 

3.  The  Bar  Photometer. — The  bar  photometer  consists  of  a 
graduated  bar  which  carries  at  one  end  a  standard  light  and  at 
the  other  end  the  test  light.     Upon  the  bar  slides  a  carriage  with 
an  apparatus  for  comparing  the  illumination  from  the  two  sources. 
The  carriage  is  to  be  moved  back  and  forth  until  the  point  is 
found  where  the  illumination  from  the  two  lights  is  equal,  and  its 
position  on  the  graduated  bar  recorded.     If  now  the  distance  of 
the  comparison  box  from  the  standard  light  be  called  "a"  and 
that  from  the  unknown  light  "b,"  then  the  illumination  of  the 
unknown  as  compared  with  the  standard  light  is  expressed  by  the 
proportion, 

unknown  _b2 
standard      a2 

There  are  many  modifications  of  this  type  of  photometer  but 
all  involve  the  four  essentials:  a  standard  light,  the  unknown 
light,  a  photometric  screen  and  a  means  of  measuring  the  distance 
of  each  light  from  the  comparison  box.  It  is  customary  to  have 
the  two  lights  fixed  at  opposite  ends  of  the  bar,  in  which  case  the 


CANDLE  POWER  OF  ILLUMINATING  GAS  121 

sum  of  a+b  in  the  preceding  formula  is  a  constant.  Some-  ' 
times  however  the  standard  lamp  is  placed  on  a  sliding  carriage 
connected  by  a  rigid  link  with  the  photometric  screen  so  that  the 
distance  "a"  of  the  formula  becomes  a  constant.  A  modification 
of  the  bar  photometer  in  use  in  England  is  the  table  photometer 
where  the  two  lights  and  the  comparison  box  are  all  rigidly  fast- 
ened at  the  points  of  a  triangle.  Comparison  is  effected  by  vary- 
ing the  rate  of  combustion  of  the  gas  being  tested  until  equality 
of  illumination  is  reached.  Its  candle-power  is  then  mathematic- 
ally determined.  This  method  of  determining  candle-power  is 
not  in  use  in  Germany  or  America. 

The  various  essential  parts  of  a  bar  photometer  will  be  con- 
sidered separately  and  the  details  of  its  operation  will  then  be 
described. 

4.  Standard  Light. — The  early  photometrists  used  as  their 
standards  candles  of  varying  size.  In  1860,  the  English  parlia- 
ment adopted  as  standard  the  sperm  candle  7/8  in.  in  diameter 
and  burning  at  the  rate  of  120  grains  per  hour.  In  1884,  Hefner 
v.  Alteneck  brought  out  the  amylacetate  lamp  which  became  a 
widely  used  standard  for  testing  the  candle-power  of  gas.  The 
Harcourt  10  candle  pentane  lamp  was  proposed  in  1898  and  has 
been  adopted  as  the  official  source  of  light  by  the  Gas  Referees  of 
London.  It  has  many  advantages.  All  of  these  flame  standards 
vary  materially  in  candle-power  with  change  in  atmospheric  con- 
ditions and  are,  for  scientific  work,  to  be  corrected  to  standard 
conditions  of  temperature,  pressure,  humidity  and  percentage  of 
carbon  dioxide  in  the  air.  In  ordinary  work  when  used  in  meas- 
uring candle-power  of  gas  flames  they  are  however  not  thus 
corrected  but  the  assumption  is  made  that  the  standard  light  and 
the  gas  light  are  equally  affected  by  atmospheric  conditions. 

The  only  satisfactory  standard  not  affected  by  atmospheric 
conditions  is  the  incandescent  electric  lamp.  Incandescent  lamps 
properly  aged  may  be  bought  with  the  certificate  of  the  Bureau 
of  Standards  and  furnish  the  most  reliable  photometric  stand- 
ards when  used  under  proper  conditions.  These  conditions,  how- 
ever, require  that  the  lamp  shall  be  supplied  with  current  at 
perfectly  definite  voltage  from  a  large  storage  battery  equipped 
with  suitable  rheostats  and  electrical  measuring  instruments  so 
that  the  installation  is  an  expensive  one,  and  is  used  only  in  re- 


122  GAS  AND  FUEL  ANALYSIS 

search  laboratories.  When  the  incandescent  electric  standard  is 
used  in  the  photometry  of  gas  flames  correction  must  be  made  for 
the  effect  of  atmospheric  conditions  on  the  flame.  This  correc- 
tion is  not  infrequently  as  much  as  ten  per  cent.,  and  has  been 
accurately  determined  for  only  a  few  of  the  standard  lights. 

6.  Photometric  Units. — The  international  candle  is  the  com- 
mon unit  of  intensity  in  England,  France  and  America,  having 
been  officially  adopted  by  agreement  of  the  government  standard- 
ising laboratories  of  the  three  countries  in  1909.  Prior  to  that 
date  the  official  unit  in  this  country  had  nominally  been  the 
British  Parliamentary  candle  but  there  had  not  been  definite 
agreement  as  to  its  value.  In  Germany  the  photometric  unit  is 
the  Hefner  which  equals  0.90  International  Candles.  Conversely 
1  International  Candle  equals  1.11  Hefners.  The  history  of  the 
adoption  of  the  International  Candle  may  be  found  in  the  reports 
of  the  Bureau  of  Standards  and  in  the  Proceedings  of  the  Ameri- 
can Gas  Institute.1 

Although  there  is  thus  an  international  unit  of  light,  the 
international  candle,  it  does  not  follow  that  this  •  unit  is  best 
obtained  by  burning  any  actual  candle.  In  fact  various  other 
standard 'lights  are  preferable. 

6.  Standard  Candles.— In  1860  the  Gas  Referees  of  the  City 
of  London  adopted  as  their  unit  the  light  emitted  by  a  sperm 
candle  of  1/6  Ib.  weight  when  burned  at  the  rate  of  120  grains  per 
hour.  From  time  to  time  they  issued  specifications  for  the  manu- 
facture of  candles  to  fulfill  this  requirement  but  were  never  suc- 
cessful in  ensuring  uniform  quality  and  in  1897  entirely  discon- 
tinued the  use  of  candles.  The  Dutch  Photometric  Commission 
reported  in  1894,  after  an  exhaustive  study,  that  the  average 
light  from  a  good  English  Parliamentary  candle  might  exceed  or 
fall  below  that  of  the  average  candle  by  nine  per  cent.  The  use 
of  candles  as  standards  is  deservedly  decreasing. 

When  candles  are  to  be  used  they  are  burned  on  a  candle 
balance  placed  on  the  photometer  bench.  A  simple  form  of 
balance  is  illustrated  in  Fig.  26.  A  long  candle  is  cut  in  two 
and  both  halves  used  simultaneously.  They  are  to  be  allowed 
to  burn  until  the  cups  have  formed  normally  and  the  wicks  have 
bent  over  till  the  tips  are  glowing  in  the  outer  flame.  The 

lProc.  Am.  Gas.  Inst.  2,  454,  528  (1907);  3,  403  (1908);  4,  78  (1909). 


CANDLE  POWER  OF  ILLUMINATING  GAS 


123 


candles  are  then  to  be  turned  so  that  the  glowing  end  of  one 
wick  points  towards  the  photometer  and  that  of  the  other  points 
in  a  direction  at  right  angles  to  that  of  the  first.  They  should 
project  1  to  1  1/2  in.  above  the  holder  and  should  burn  clearly  and 
without  guttering.  When  all  is  in  readiness  for  a  test,  the 
counterpoises  are  adjusted  so  that  the  candles  are  slightly  too 
heavy  for  a  perfect  balance.  As  they  burn  away  the  pointer 
on  the  scale  falls  and  as  it  passes  the  zero  mark  the  stop  watch  is 
started.  A  20-grain  weight  is  then  placed  on  the  pan  below  the 
candles  and  photometric  readings  are  made  each  half-minute. 
At  the  expiration  of  four  and 
a  half  minutes  the  observer 
returns  to  the  candle  balance 
and  stops  the  watch  when  the 
pointer  again  is  at  the  zero 
mark,  indicating  that  the  20 
grains  of  sperm  have  been 
burned.  If  the  candles  are 
burning  at  exactly  the  proper 
rate  the  watch  should  show 
that  exactly  five  minutes  have 
elapsed.  If  the  variation  in 
the  amount  of  sperm  burned 
per  hour  is  not  over  5  per  cent, 
from  the  standard  amount  it  is 
permissible  to  make  a  mathe- 
matical correction,  the  as- 
sumption being  that  the  light  evolved  is  in  direct  proportion  to  the 
weight  of  candles  burned .  If  the  observed  weight  of  sperm  burned 
by  the  two  candles  is  250  grains  per  hour  instead  of  240  the  value 

250 

of  the  light  is  said  to  be  2  X  ^  =  2.08  candles.  If  the  devia- 
tion is  greater  than  5  per  cent,  the  test  must  be  rejected  and  a 
different  candle  used.  Improper  ventilation  and  too  high  a 
temperature  in  the  photometer  room  will  affect  the  burning  of 
the  candles.  This  subject  is  discussed  in  §  18. 

7.  The  Hefner  Lamp. — The  dimensions  of  the  Hefner  lamp 
have  been  rigidly  specified  by  the  German  Reichsanstalt1  which 

1  Jour,  fur  GasbeL,  36,  341  (1893). 


FIG.  26. — Candle  balance. 


124 


GAS  AND  FUEL  ANALYSIS 


will  certify  a  lamp  to  be  correct  if  it  is  properly  made  mechanic- 
ally and  gives  a  light  which  does  not  differ  more  than  2  per  cent. 
from  the  official  lamp  of  the  Reichsanstalt.  The  construction 
of  the  lamp  is  shown  in  Fig.  27.  It  consists  of  a  brass  bowl 
into  which  a  head  screws  carrying  the  German  silver  wick  tube 
and  the  mechanism  for  controlling  the  height  of  the  flame. 
The  flame  height  is  determined  by  a  gage  which  clamps  to  the 
head-piece.  The  older  form  engage  shown  at  A  consists  of  two 
sights,  one  on  each  side  of  the  flame.  The  newer  Krtiss  optical 
gage  shown  at  C  consists  of  a  ground  glass  screen  and  a  magnify- 


FIG.  27.  —  Hefner  lamp. 


ing  lens  which  allows  more  delicate  adjustment  of  the  flame  tip 
to  the  horizontal  line  across  the  gage.  Each  lamp  is  provided 
with  a  control  gage  shown  at  B  which  fits  over  the  wick  tube 
and  sits  squarely  on  the  head-piece.  With  the  control  gage  in 
this  position  and  the  lamp  level  an  observer  looking  toward  the 
light  should  see  through  the  openings  D  a  very  fine  ray  of  light 
less  than  0.  1  mm.  wide  between  the  top  of  the  wick  tube  and  the 
control  gage,  and  looking  through  the  optical  gage  should  see 
the  cross-hair  in  exact  coincidence  with  the  broad  top  of  the 
control  gage.  The  wick  tube  is  screwed  into  the  head-piece 
and  if  it  becomes  necessary  to  change  its  height  the  control  gage, 


CANDLE  POWER  OF  ILLUMINATING  GAS  125 

1  inverted,  is  to  be  pushed  down  the  wick  tube  and  used  as  a  handle. 
The  exact  material  of  which  the  wick  is  made  is  not  of  importance 
but  it  must  fill  the  tube  snugly  but  not  tightly.  It  is  best  to  use 
only  that  furnished  by  the  manufacturers.  The  amyl  acetate 
must  be  of  good  quality  and  certified  to  be  fit  for  photometrical 
purposes. 

In  using  the  Hefner  lamp  the  bowl  is  to  be  filled  about  two- 
thirds  full  of  amyl  acetate  and  after  the  wick  has  been  moistened 
by  capillary  action  it  is  to  be  screwed  somewhat  above  the  wick 
tube  and  cut  squarely  off.  The  lamp  is  then  to  be  lighted  and 
allowed  to  burn  at  least  ten  minutes  with  occasional  regulation 
of  the  flame  height  before  a  test  is  commenced.  The  temperature 
of  the  photometer  room  should  be  between  60°  and  70°  F.  The 
lamp  is  to  sit  on  a  horizontal  support  in  a  room  free  from  drafts 
and  adequately  ventilated. 

The  flame  height  of  the  Hefner  lamp  is  to  be  carefully  adjusted 
since  a  deviation  of  1  mm.  from  the  correct  flame  height  of  40, 
introduces  an  error  of  about  3  per  cent.  It  is  the  luminous  tip 
of  the  flame  which  is  to  be  40  mm.  high.  With  the  Kriiss  optical 
gage  the  frosted  glass  cuts  out  the  almost  colorless  outer  flame  so 
that  there  is  no  possibility  of  confusion.  With  the  older  Hefner 
gage  the  luminous  tip  should  appear  tangent  to  the  lower  edge 
of  the  sighting  plane. 

If  the  lamp  is  used  only  infrequently  it  should  be  emptied 
after  use  and  both  lamp  and  wick  should  be  washed  with  alcohol. 
It  is  wise  to  throw  away  the  old  amyl  acetate  and  clean  the  lamp 
in  this  manner  at  intervals  even  when  it  is  in  frequent  use  since 
the  amyl  acetate  decomposes  somewhat  on  standing. 

The  Hefner  lamp  gives  a  light  of.  0.9  international  candles 
when  burned  in  pure  air  under  760  mm.  barometric  pressure  and 
containing  8.8  liters  of  water  vapor  per  cubic  meter.  Although 
atmospheric  conditions  must  be  controlled  and  correction  made 
in  exact  scientific  work  corrections  are  usually  omitted  in  taking 
candle-power  of  gas  on  the  assumption  that  atmospheric  condi- 
tions affect  the  Hefner  lamp  and  the  gas  burner  to  a  similar  de- 
gree. The  errors  involved  in  this  assumption  are  discussed  briefly 
in  §  18.  The  Hefner  lamp  is  a  widely  used  standard.  It  is 
portable,  cheap,  and  relatively  accurate.  Its  disadvantage  is  its 


126 


GAS  AND  FUEL  ANALYSIS 


low  candlepower,  and  the  tendency  of  the  flame  to  flicker,  es- 
pecially at  summer  temperature. 

8.  The  Pentane  Lamp. — The    10    candle   pentane   lamp   or 

Harcourt  lamp  was  adopted  as  stand- 
ard by  the  London  Gas  Referees  in 
1898. l 

Fig.  28  shows  this  lamp  with  some 
improvements  in  details  recommended 
by  the  Bureau  of  Standards  and  added 
by  the  American  manufacturers.  In 
this  lamp  air  entering  at  A  passes  over 
pentane  and  becomes  saturated  with 
pentane  vapor.  The  air-gas  so  formed 
descends  by  gravity  to  an  Argand 
burner  B  enclosed  in  a  metal  hood. 
The  flame  is  drawn  into  a  definite 
form  and  the  top  of  it  is  hidden  from 
view  by  a  long  brass  chimney  C.  The 
chimney  is  surrounded  by  a  larger 
brass  tube  D  in  which  air,  warmed  by 
the  chimney,  rises  and  descends 
through  the  tube  E,  which  is  also  the 
main  standard  of  the  lamp,  to  the  cen- 
ter of  the  Argand  burner  where  it  aids 
in  the  combustion  of  the  gas.  The 
lamp  may  be  obtained  with  the  cer- 
tificate of  the  Bureau  of  Standards. 

Before  using  the  lamp  the  satu- 
rator  is  to  be  filled  about  two-thirds 
full  of  pentane  and  both  cocks  on  the 
saturator  are  to  be  closed.  As  pen- 
tane is  very  volatile  and  mixtures  of  its  vapor  and  air  within 
certain  proportions  are  explosive  care  must  be  taken  that  no 
flames  are  burning  in  the  room  while  the  lamp  is  being  filled. 
The  inner  chimney  above  the  burner  must  be  centered  by 
the  adjusting  screws,  turned  so  that  the  mica  window  is  away 
from  the  photometer  box  and  set  at  the  proper  height  by  plac- 
ing on  the  burner  the  47  mm.  block  which  accompanies  the 
lJour.  of  Gas  Lighting,  71,  1252  (1898). 


FIG.  28. — 10  candle  power 
pentane  lamp. 


CANDLE  POWER  OF  ILLUMINATING  GAS  127 

lamp,  and  lowering  the  chimney  till  it  rests  lightly  on  the  block. 
To  prepare  the  lamp  foT  lighting,  open  the  outlet  cock  on  the 
saturator  and  the  drip  cock.  This  will  fill  the  feed  pipe  with  pen- 
tane  vapor  and  air.  Open  the  inlet  cock  on  the  saturator,  close 
the  drip  cock,  open  the  regulating  cock  at  the  burner  and  light  the 
gas  at  once.  It  requires  about  fifteen  minutes  for  the  flame  to 
become  constant  and  during  this  period  the  top  of  the  flame  should 
be  kept  approximately  on  the  cross  bar  of  the  mica  window. 
The  lamp  should  be  set  for  maximum  luminosity  which  condition 
is  attained  when  the  flame  is  just  high  enough  so  that  the  non- 
luminous  upper  portion  is  cut  off  from  the  photometric  screen  by 
the  chimney.  In  case  of  doubt  the  proper  setting  may  be  deter- 
mined by  lighting  the  gas  flame  at  the  other  end  of  the  bench 
and  determining  with  the  photometer  the  setting  of  the  lamp 
which  gives  maximum  illumination. 

In  leaving  the  lamp  after  a  test  both  the  inlet  and  the  outlet 
cocks  of  the  saturator  should  be  closed.  After  about  a  gallon  of 
pentane  has  been  burned  the  liquid  remaining  in  the  saturator 
should  be  emptied  out  and  thrown  away. 

9.  Secondary  Standards  of  Light. — The  Hefner  lamp,  the  10 
Candle  Pentane  lamp  and,  to  a  lesser  degree,  standard  candles 
are  primary  standards  since  they  are  readily,  if  not  entirely  ac- 
curately, reproducible.  There  are  various  secondary  standards 
which  are  convenient  to  use  when  frequent  candle-power  deter- 
minations are  to  be  made  but  which  must  be  standardized  at 
intervals  by  direct  comparison  with  a  primary  standard.  Most 
of  these  standards  are  based  on  the  fact  that  the  brightest  por- 
tion of^a  lamp  flame  is  of  almost  constant  luminosity. 

The"fedgerton  Standard  burner  consists  of  a  Sugg  "D"  burner 
provided  with  a  glass  chimney  1  3/4  in.  in  diameter  and  7  in. 
high.  Outside  of  this  glass  chimney  is  a  brass  sleeve  with  a 
horizontal  slot  13/32  of  an  inch  high  through  which  the  light 
passes  to  the  photometer.  This  is  nominally  a  five  candle-power 
standard  but  will  actually  vary  from  four  to  seven  candles. 
After  the  value  with  a  given  gas  has  been  fixed  it  will  not  vary 
much  if  the  candle-power  of  the  gas  feeding  it  does  not  vary  over 
two  candles.  The  chimney  must  be  cleaned  frequently  and  the 
lamp  restandardized  each  time  a  new  chimney  is  put  into  service. 

The  Elliot  lamp  is  a  student  lamp  of  special  design  with  a 


128 


GAS  AND  FUEL  ANALYSIS 


flat  wick  and  a  rather  large  chimney  and  a  screen  which  cuts  off 
all  but  the  desired  portion  of  the  flame.  The  lamp  uses  kerosene 
as  its  fuel  and  is  nominally  a  ten  candle-power  lamp.  Its  illu- 
minating value  with  a  single  lot  of  good  kerosene  is  of  very  satis- 
factory constancy. 

10.  Standard  Gas  Burners. — At  the  time  when  gas  testing 
commenced  to  be  standardized  the  Argand  burner  was  the  form 
in  common  use.  This  type  was  therefore  naturally  adopted  as 
the  standard.  It  was  also  recognized  that  it  was  only  right  to 


FIG.  29.— D  Argand 
burner. 


FIG.  30. — Metropolitan 
No.  2  Argand  burner. 


test  the  gas  in  a  burner  which  was  adapted  to  it  and  therefore 
various  standards  came  into  vogue  in  England,  such  as  the  Sugg 
D  Argand  illustrated  in  Fig.  29,  which  is  intended  for  gases 
of  less  than  16  candle-power.  The  Sugg  F  burner  is  intended  for 
gases  of  16-20  candle-power. 

In  1905,  in  connection  with  a  readjustment  of  the  price  and 
candle-power  of  the  gas  supplied  in  London  the  Gas  Referees 
were  directed  by  Parliament  to  use  a  burner  adapted  to  obtain 
from  the  gas  the  greatest  amount  of  light  when  burned  at  the 
rate  of  five  cubic  feet  per  hour.  In  accordance  with  these  instruc- 


CANDLE  POWER  OF  ILLUMINATING  GAS  129 

tions  the  Gas  Referees  adopted  the  Metropolitan  No.  2  Burner 
shown  in  Fig.  30.  This  burner  differs  from  the  older  types 
mainly  in  having  an  adjustable  air  supply  to  the  center  of  the 
burner.  The  burner  is  designed  for  all  qualities  of  gas  up  to  20 
candle-power.  When  lighting  the  burner  the  air  regulating  disc 
A  is  to  be  screwed  down  so  that  the  full  supply  of  air  passes  to  the 
burner,  and  the  burner  is  to  be  adjusted  to  approximately  the  five 
cubic  foot  rate.  After  allowing  it  to  burn  for  fifteen  minutes  to 
become  thoroughly  warm  the  gas  is  to  be  adjusted  carefully 
to  the  rate  of  5  cu.  ft.  an  hour,  after  which  the  air  regulator  is  to 
be  screwed  upwards  until  the  flame  rises  in  the  chimney  as  high 
as  possible  without  smoking.  The  Metropolitan  No.  2  Argand 
gives  results  materially  higher  than  the  ordinary  Argand  on 
gases  of  low  candle-power. 

Bray's  No.  7  Slit  Union  burner  is  frequently  used  with  car- 
buretted  water  gas  of  more  than  20  candle-power.  The  rate  of 
gas  consumption  is  as  usual  adjusted  to  5  cu.  ft.  an  hour. 

11.  The    Bunsen  and    Leeson    Photometric    Screens. — The 
Bunsen  photometric  disc  dates  from  1841  and  in  its  simplest 
form  consists  merely  of  a  sheet  of  paper  with  a  grease  spot  in  the 
center.     This  is  mounted  so  that  it  may  be  moved  back  and  forth 
between  the  two  lights.     When  looking  toward  the  stronger  light 
the  translucent  grease  spot  appears  bright.     As  the  carriage  is 
slowly  moved  away  from  the  stronger  light  the  constrast  between 
the  spot  and  the  surrounding  paper  diminishes  and  almost  dis- 
appears when  equality  of  illumination  is  reached.     If  the  carriage 
is  moved  still  further  in  the  same  direction  the  grease  spot  stands 
out  dark  against  the  white  background.     The  paper  screen  is 
usually  mounted  in  a  box  as  shown  in  Fig.  34  where  by  an 
arrangement  of  mirrors 'the  observer  standing  in  front  of  the 
instrument  may  see  both  sides  of  the  screen  at  once.     This  form 
of  apparatus  is  still  frequently  used. 

The  Leeson  star  disc  is  a  modification  of  the  Bunsen  screen. 
It  consists  of  a  piece  of  opaque  paper  from  whose  center  is  cut 
a  star  and  which  is  pressed  between  two  sheets  of  translucent 
paper. 

12.  The  Lummer-Brodhun  Photometric  Screen. — This  is  a 
very  accurate  form  of  photometer  which  is  shown  diagrammatic- 
ally  in  Fig.   31   and    in    perspective    in  Fig.   32.     It  consists 


130 


GAS  AND  FUEL  ANALYSIS 


of  a  series  of  reflecting  surfaces  and  prisms  which  direct  light  rays 
from  the  two  sources  into  a  telescope  tube.  Light  entering  from 
the  two  opposite  sources  R  and  L  is  diffusely  reflected  by  the 


b-" 


FIG.  31. — Diagram  of  Lummer-Brodhun  photometric  screen. 

opaque  plaster  of  paris  disc  P  onto  the  mirrors  MI  and  M2  and 
by  them  to  the  prisms  AB.     The  prism  A  has  most  of  its  hypothe- 


Fia.  32. — Lummer-Brodhun  photometric  screen. 

nusal  face  ground  away,  o.nly  a  small  circular  plane  being  left  in 
the  center.  The  two  prisms  are  clamped  closely  together  and 
become  optically  homogeneous  over  this  small  circular  area  shown 


CANDLE  POWER  OF  ILUMINATING  GAS 


131 


FIG.  33.— Field  of 
Lummer -B  r  o  d  h  u  n 
contrast  photomet- 
ric screen. 


at  ab.  Of  the  light  coming  from  L  only  that  reaches  the  telescope 
which  passes  through  this  circular  spot,  the  path  of  the  rays  being 
shown  from  L2.  Of  the  light  from  R,  that  which  strikes  the  spot 
ab  passes  on  undeflected  and  is  absorbed  by  the  black  walls  of  the 
box.  The  path  of  these  rays  is  shown  from  R2.  The  other  rays 
suffer  total  reflection  into  the  telescope  as  shown  in  the  rays  from 
RI.  The  image  in  the  telescope  appears,  therefore,  as  a  circular 
spot  illuminated  from  L  in  a  circular  field  illuminated  from  R.  In 
this  equality  photometer  when  the  illumination  from  the  two 
sources  is  identical  the  spot  and  the  field  are 
not  to  be  distinguished  from  one  another. 

In  the  Lummer-Brodhun  contrast  photom- 
eter advantage  is  taken  of  the  physiological 
fact  that  the  eye  is  able  to  perceive  a  smaller 
degree  of  difference  in  contrast  than  difference 
in  brightness.  By  suitably  cutting  the  prisms 
the  image  in  the  telescope  is  divided  into  four 
portions  as  shown  in  Fig.  33.  In  this  figure 
the  shaded  trapezoidal  space  A'  is  illuminated 
from  the  same  source  as  the  shaded  semi-circular  area  A.  Simi- 
larly B  and  B'  are  illuminated  from  the  same  source.  However, 
although  the  areas  A  and  A'  are  illuminated  from  the  same  source, 
they  are  not  equally  illuminated,  for  through  the  interposition  of 
a  plate  of  glass  before  A'  it  receives  about  four  per  cent,  less  light 
than  A.  B'  is  in  the  same  way  and  to  the  same  degree  less 
brilliantly  illuminated  than  B. 

If ,  now,  the  light  from  the  two  sources  is  exactly  the  same  both 
in  intensity  and  color  the  semi-circular  fields  A  and  B  will  be 
identically  illuminated  and  will  not  be  distinguishable  from  one 
another.  The  trapezoidal  figures  A'  and  B'  will  also  be  identi- 
cally illuminated  and  will  stand  out  with  the  same  relief  from  their 
respective  backgrounds.  This  can  only  happen  when  A  and  B 
are  equally  illuminated.  It  affords  a  more  sensitive  ocular  test 
of  the  equality  of  A  and  B  than  can  be  obtained  by  comparing 
them  directly.  The  lights  at  the  two  ends  of  the  bench  are  never 
of  absolutely  the  same,  and  are  sometimes  of  a  widely  differing, 
color.  When  a  Welsbach  light  is  tested  against  the  Hefner  lamp 
the  field  illuminated  from  the  mantle  burner  is  a  clear  blue  color 
while  the  other  is  a  yellow.  The  eye  cannot  determine  with  much 


132  GAS  AND  FUEL  ANALYSIS 

accuracy  when  the  yellow  field  and  the  blue  one  are  illuminated 
to  the  same  extent,  but  it  can  determine  with  greater  accuracy 
when  the  yellow  trapezoid  A'  stands  out  from  its  blue  background 
with  the  same  distinctness  that  the  blue  trapezoid  B'  stands  out 
from  its  yellow  background.  The  eye  judges  slight  contrasts 
more  accurately  than  large  ones  and  therefore  it  is  most  sensitive 
when  the  photometer  is  almost  at  the  neutral  point.  It  is  well 
to  make  an  approximate  setting  for  equality  of  A  and  B  and  then 
focus  the  attention  on  the  contrast  between  the  trapezoids  and 
their  respective  backgrounds  and  complete  the  adjustment. 

13.  The  Flicker  Photometer. — In  the  various  forms  of  flicker 
photometer  the  light  from  each  source  is  presented  alternately 
and  rapidly  to  the  eye  by  means  of  revolving  discs  or  prisms  in 
the  photometer  box.     When  the  intensity  of  light  from  the  two 
sources  is  the  same  the  flicker  vanishes.     No  difficulty  is  experi- 
enced with  lights  of  varying  colors,  but  the  photometer  is  fa- 
tiguing to  the  eye  and  its  proper  adjustment  requires  consid- 
erable skill. 

14.  The  Gas  Meter. — The  meters  used  in  photometric  work 
are  of  the  same  general  type  of  wet  meter  as  those  described  in 
§  3  of  Chapter  VII  for  calorimetric  work.     They  must  be  cali- 
brated with  the  same  care  and  used  with  the  same  precautions. 
It  is  more  convenient,  however,  to  use  a  smaller  meter  which 
passes  only  1/12  cu.  ft.  per  revolution.     When  the  gas  is  being 
burned  at  the  rate  of  5  cu.  ft.  an  hour  this  meter  will  make  exactly 
one  revolution  a  minute.     The  dial  of  the  meter  is  graduated  into 
five  parts  with  finer  subdivisions.     An  observation  of  one  minute 
will  therefore  give  directly  the  uncorrected  gas  consumption  in 
cubic  feet  per  hour.     Great  care  must  be  taken  to  see  that  the 
water  of  the  meter  is  saturated  with  gas  of  the  sort  that  is  to  be 
tested,  for  the  "  illuminants "  of  the  gas  are  relatively  soluble  in 
water  and  a  slight  change  in  their  percentage  makes  an  appreci- 
able difference  in  the  candle-power  of  the  gas. 

16.  The  Photometer  Bench  and  Its  Equipment. — The  preceding 
sections  have  discussed  the  various  types  of  standard  lights, 
burners  and  photometers  which  may  be  used.  It  is  evident  that 
wide  latitude  may  be  exercised  in  the  choice  of  units  and  the 
method  of  assembling  them  to  form  a  photometer  bench. 

The  details  regarding  the  length  of  bar,  type  of  standard  light, 


CANDLE  POWER  OF  ILLUMINATING  GAS 


133 


form  of  test  burner,  kind  of  comparison  box,  and  the  directions 
for  testing  are  in  some  cases  controlled  by  legal  enactment  and  are 
in  some  cases  matters  of  arbitrary  choice.  It  is  under  all  cir- 
cumstances necessary  that  the  meter,  standard  light,  and  gas 
burner  be  thoroughly  reliable.  The  photometric  screen  may  be 
of  cheaper  type  and  the  bench  itself  may  be  of  simple  wooden 
construction  with  the  scale  made  of  yard  sticks  joined  together. 
The  bar  most  commonly  used  in  America  is  60  inches  long.  This 
is  sufficiently  accurate  where  ordinary  gas  flames  are  being  tested. 
For  lamps  of  high  candle-power  longer  bars  are  desirable. 


FIG.  34. — Photometer  bench. 

A  photometer  bench  frequently  used  is  shown  in  Fig.  34. 
At  the  right  hand  end  is  shown  the  meter  and  next  to  it  the  candle 
balances  in  position,  with  the  Edgerton  standard  burner  on  a 
swinging  arm  so  that  it  may  be  used  instead  of  the  candles.  At 
the  left  hand  end  is  the  Argand  burner  for  the  gas  and  between 
the  two  the  bar  itself  with  its  screens  and  photometer.  The 
piping  for  the  gas  is  entirely  below  the  table  top  but  the  pressure 
regulators  and  gages  are  shown  above  the  table  at  the  back. 

Precision  photometers  usually  follow  the  German,  or  Reichs- 


134  GAS  AND  FUEL  ANALYSIS 

anstalt,  pattern  in  which  the  bar  is  built  up  of  a  rigid  steel  track 
on  which  the  carriage  of  the  photometric  screen  travels.  The 
standard  light  and  the  test  light  are  usually  also  mounted  on  a 
travelling  carriage  with  provision  for  clamping  them  rigidly  at 
any  desired  point  of  the  bench.  The  length  of  the  bench  may 
thus  be  varied  at  will. 

16.  Details  of  a  Test. — The  details  of  a  test  will  of  course  vary 
with  the  equipment  of  the  photometer  bench  and  especially  with 
the  type  of  standard  light  employed.  Directions  for  the  use  of 
these  lights  have  been  given  in  preceding  sections.  In  the  follow- 
ing paragraphs  will  be  found  general  directions  which  are  appli- 
cable to  most  forms  of  apparatus. 

The  meter  is  to  be  examined  to  see  that  the  water-level  is 
correct  and  if  necessary  more  water  is  to  be  added.  In  case 
the  test  is  unusually  important  the  meter  should  be  calibrated 
against  a  tank  of  known  volume.  The  tightness  of  connections 
between  the  meter  and  the  burner  is  to  be  assured  by  turning  the 
gas  into  the  meter  while  keeping  the  stopcock  on  the  burner 
closed.  The  meter  hand  should  not  show  any  perceptible  motion 
in  one  minute.  If  there  is  a  small  leak  allowance  may  be  made 
for  it  in  the  calculations,  but  it  is  vastly  better  to  have  the  whole 
apparatus  tight. 

A  clean  chimney  is  to  be  placed  on  the  Argand  burner  and  the 
burner  lighted.  The  pressure  gage  between  the  diaphragm 
governor  and  the  burner  should  indicate  about  1  in.  of  water  pres- 
sure depending  on  the  exact  type  of  burner  used.  The  consump- 
tion of  gas  is  to  be  set  so  that  the  meter  hand  makes  a  revolution 
in  approximately  a  minute  and  the  light  is  then  allowed  to  burn 
for  at  least  fifteen  minutes.  If  the  meter  has  had  much  fresh 
water  added  to  it,  or  if  it  was  last  used  for  a  gas  of  a  different 
quality  than  the  one  soon  to  be  tested,  or  if  the  gas  is  being  drawn 
from  long  lengths  of  pipes  where  the  gas  lies  dead,  a  longer  time 
than  fifteen  minutes  must  be  allowed  to  elapse  before  commencing 
the  test  which  must  not  be  started  until  it  is  certain  that  the  gas 
burning  is  of  representative  quality  and  that  it  has  not  been 
changed  by  contact  with  the  water  of  the  meter. 

The  final  adjustment  of  the  gas  is  made  after  taking  into  con- 
sideration the  meter  temperature  and  the  barometric  pressure. 
The  desired  rate  of  consumption  being  5  cu.  ft.  measured  under 


CANDLE  POWER  OF  ILLUMINATING  GAS  135 

standard  conditions,  the  correct  apparent  rate  may  be  mentally 
calculated  by  adding  to  the  5  ft.  0.01  cu.  ft.  for  each  degree 
Fahrenheit  shown  by  the  meter  thermometer  above  60,  and  add- 
ing 0.03  ft.  for  each  0.1  in.  of  mercury  pressure  below  30.  For 
example,  if  the  meter  temperature  is  80°  F.,  and  the  barometric 
reading  is  29.5  the  uncorrected  consumption  of  gas  per  hour 
should  be  5.0+.20+.  15  =  5.35.  The  gas  is  to  be  set  to  this 
desired  flow  with  an  error  of  less  than  1/10  cu.  ft..  The  stop- 
watch is  started  as  the  hand  crosses  the  zero  and  stopped  after 
one  complete  revolution.  It  should  read  between  59  and  61 
seconds.  After  the  gas  has  been  satisfactorily  adjusted  and 
the  standard  lamp  given  a  final  adjustment  the  test  may  be 
commenced. 

The  observer  starts  the  stopwatch  as  the  large  hand  of  the 
meter  passes  the  zero  and  steps  quietly  to  the  photometer  avoid- 
ing sudden  movements  which  would  create  drafts,  and  makes  and 
records  the  first  observation.  Four  more  readings  are  made  at 
intervals  of  about  twenty  seconds  and  then  the  photometric 
screen  is  reversed  and  five  similar  readings  taken.  If  the  lights 
flicker  during  an  adjustment  the  observer  must  wait  until  the 
drafts  have  subsided  before  completing  the  observation.  The 
series  of  ten  observations  usually  requires  about  five  minutes. 
At  their  conclusion  the  operator  steps  back  to  the  meter  and  stops 
the  watch  as  the  large  hand  of  the  meter  again  passes  the 
zero. 

If  a  stopwatch  is  not  available  it  is  better  to  make  the  test 
during  an  even  number  of  minutes  rather  than  during  the  con- 
sumption of  an  even  number  of  cubic  feet  of  gas.  If  the  observer 
holds  the  watch  close  to  the  meter  and  keeps  his  eyes  on  the  watch 
till  the  second  hand  reaches  the  zero  and  then  reads  the  position 
of  the  large  meter  hand,  and  follows  the  same  procedure  at  the 
close  of  the  test,  the  error  will  be  well  within  the  other  necessary 
errors  of  the  process.  In  case  a  stopwatch  is  available,  it  is  more 
accurate  to  start  the  watch  as  the  meter  hand  comes  to  its  zero 
and  to  conclude  the  observation  when  the  meter  hand  passes  its 
zero,  after  the  photometric  observations  have  been  completed. 

17.  Illustration  of  Calculation. — The  calculation  which  follows 
is  for  a  test  made  on  a  2500  mm.  bench  with  a  Hefner  light  as  the 
standard. 


136*  GAS  AND  FUEL  ANALYSIS 

Date,  Feb.  26 

Source  of  Gas.     Proportional  Tank.     Test  42.     Experimental  Gas  Plant. 

Gas  burned  in  London  Argand. 

Standard  Light — Hefner. 

Time  Meter  Reading 

Commencement  of  Test   10  :  16  :  00  A.  M  47 . 8 

End  of  test  10:21:00  50+24.6=74.6 


Duration  5  :  00 

Difference  in  meter  readings 26 . 8 

Cubic  feet  gas  per  hour  uncorrected 5 . 36 

Meter  Temperature  80°  F.     Error  in  meter  less  than  0 . 1  per  cent. 

Barometer  29 . 5  inches.     Correction  factor 0 . 930 

Cubic  feet  gas  per  hour  uncorrected  5.36.     Corrected 4.98 

Bar  Readings         454,  456,  455,  462,  460 

460,  458,  460,  463,  464  Average  462. 

,11.-       r(2500-462)2    XI     5.00 
Calculation  [       (462)2          79J  X4T98==17'6  candle-P°wer- 

18.  The  Photometer  Room. — The  photometer  bench  must  be 
placed  in  a  room  of  reasonably  constant  temperature  which  is 
free  from  drafts  and  yet  well  ventilated.  A  room  ventilated  so 
that  the  carbon  dioxide  does  not  rise  above  ten  parts  in  10,000 
during  a  test  is  as  much  as  can  be  expected  in  ordinary  work. 
The  carbon  dioxide  may  rise  to  twenty  parts  without  the  air 
being  more  polluted  than  in  an  ordinary  crowded  street  car  in 
winter.  The  water  vapor  normally  present  in  the  air  and  that 
given  off  by  the  flames  and  the  respiration  of  persons  in  the 
photometer  room  exerts  an  even  greater  influence  on  flames  than 
the  carbon  dioxide  but  since  its  accurate  determination  is  difficult, 
the  carbon  dioxide  is  usually  taken  as  the  measure  of  contamina- 
tion of  the  air. 

The  committee  on  Photometry  of  the  American  Gas  Institute1 
has  published  some  curves  showing  the  variation  of  certain 
flames  with  increased  carbon  dioxide  when  compared  with  an 
incandescent  electric  lamp.  The  humidity  of  the  air  varied  so 
much  from  day  to  day  that  a  comparison  of  one  day's  work  with 
another  could  not  be  made  and  the  following  figures  from  their 
curves  must  be  taken  as  merely  illustrative  of  the  large  errors 
that  may  arise. 

lProc.  Am.  Gas.  Inst.,  11,  480  (1907). 


CANDLE  POWER  OF  ILLUMINATING  GAS  137 

COMPARISON  OF  PENTANE  LAMP  WITH  GAS  FLAME 

Parts  CO2  in  10,000 10.0     20.0 

Per  cent,  loss  of  candle-power  of  gas  flame 4.0     20.0 

Per  cent,  loss  of  candle-power  of  pentane  flame 7.5     31. 0 

COMPARISON  OF  PENTANE  LAMP  WITH  CANDLES 

Parts  CO2  in  10,000 10.0     20.0 

Per  cent,  loss  of  candle  power  of  candles 19.0     27. 0 

Per  cent,  loss  of  candle  power  of  pentane  flame 13 . 0     16.5 

It  is  therefore  evident  that  the  usual  assumption  that  the 
standard  light  and  the  test  light  are  equally  affected  by  atmos- 
pheric conditions,  is  erroneous  and  that  care  should  be  taken  to 
have  the  test  made  under  as  favorable  atmospheric  conditions 
as  possible. 

19.  Jet  Photometers. — There  are  two  main  types  of  jet  pho- 
tometers.    In  one  type,  gas  passes  through  a  pressure  regu- 
lator and  issues  at  constant  pressure  through  a  small  round 
orifice  where  it  burns  in  a  jet  whose  height  as  read  on  the  glass 
chimney  is  assumed  to  give  candle  power  directly.     In  the  other 
type  of  jet  photometer  the  gas  flame  is  kept  at  a  constant  height 
and  the  pressure  required  to  force  the  gas  through  the  burner 
opening  is  measured  as  an  indication  of  candle  power.     No  type 
of  jet  photometer  can  be  relied  on  to  do  more  than  give  approxi- 
mate  determinations.     They  should   be   calibrated   frequently 
against  a  bar  photometer. 

20.  Accuracy  of  Photometric  Work. — When  it  is  recalled  that 
a  Hefner  lamp  is  considered  as  correct  if  it  is  within  2  per  cent, 
of  the  standard,  and  that  the  absolute  value  of  the  pentane 
lamp  may  vary  as  much  as  25  per  cent.1  in  the  course  of  a  year 
on  account  of  changing  atmospheric  conditions  and  further  that 
the  human  eye  is  a  very  inaccurate  scientific  instrument,  a  greater 
accuracy  than  half  a  candle  can  hardly  be  expected  with  illumi- 
nating gas  tested  under  ordinary  conditions.     Much  larger  errors 
may  creep  in  unless  care  is  taken. 

1  J.  B.  Klumpp,  Proc.  Am.  Gas  Light  Assoc.,  1905.    Appendix. 


CHAPTER  IX 
ESTIMATION  OF  SUSPENDED  PARTICLES  IN  GAS 

1.  Introduction. — The  estimation  of  particles  held  in  suspen- 
sion in  gases  is  daily  becoming  of  greater  importance  on  account 
of  legal  restrictions  on  pollution  of  the  air  and  on  account  of 
insistence  on  closer  control  of  industrial  operations  by  manu- 
facturers.    The  problem  is  one  of  great  difficulty  and  is  usually 
susceptible  of  only  approximate  solution.     Not  only  is  it  difficult 
to  obtain  the  suspended  solids  present  in  a  flue  at  a  given  point 
and  time,  but  it  is  difficult  to  determine  whether  the  solids  thus 
determined  were  normal  in  amount  or  whether  they  were,  for 
instance,  low  because  of  the  deposition  of  an  unusually  large  pro- 
portion prior  to  the  point  of  sampling  on  account  of  slower  veloc- 
ity of  gas  in  the  main,  or  because  of  lower  temperature  or  for  some 
other  reason. 

2.  The  Distribution  of  Particles  in  the  Cross-section   of  a 
Straight  Main. — If  the  main  is  horizontal  it  is  evident  that  there 
will  tend  to  be  a  stratification  of  the  particles,  the  large  and  heavy 
particles  separating  faster  than  the  fine  and  light.     This  tendency 
to  settle  is,  however,  resisted  by  the  whirling  motion  which 
gases  traversing  flues  frequently  possess  and  which  is  frequently 
caused  by  the  inequalities  in  pressure  produced  by  bends  in  the 
pipe.     The  velocity  of  gas  in  a  straight  main  at  ordinary  working 
speeds  is  greatest  at  the  center  and  least  at  the  walls.     The 
shape  of  the  wave  front  varies  with  the  speed  of  the  gas,  high 
velocities  accentuating  the  difference.     Solid  particles  are  pushed 
gradually  out  of  the  zone  of  high  velocity  into  one  of  lower 
velocity  in  the  same  way  that  a  piece  of  wood  in  a  river  is  grad- 
ually pushed  to  the  still  waters  along  the  bank.     This  action 
takes  place  in  a  vertical  as  well  as  a  horizontal  main. 

The  solids  contained  in  a  gas  at  the  point  of  greatest  velocity 
will  therefore  be  the  least  in  amount,  the  smallest  in  size,  and  the 
lowest  in  specific  gravity.  The  quantity  of  particles,  their  size 
and  specific  gravity  will  all  increase  in  the  regions  where  velocity 

138 


ESTIMATION  OF  SUSPENDED  PARTICLES  IN  GAS      139 

is  least.  In  a  normal  round  main  this  point  of  greatest  velocity 
is  the  center  where  will  be  found  the  fewest  and  lightest  solid 
particles.  Their  quantity  and  magnitude  increase  in  successive 
rings  to  the  circumference.  If  the  velocity  of  the  gas  is  decreased 
until  the  main  is  also  acting  as  a  settling  chamber  there  will  be 
little  difference  in  the  velocity  throughout  the  cross-section  and 
the  region  near  the  top  of  the  main  will  contain  the  fewest  solid 
particles. 

This  uneven  distribution  of  suspended  particles  in  a  gas 
stream  may  take  place  very  rapidly  as  was  shown  by  the  author1 
some  years  ago  in  an  attempt  to  determine  the  amount  of  sus- 
pended tar  in  unpurified  illuminating  gas.  A  14-in.  main  con- 
taining unpurified  illuminating  gas  was  tapped  on  its  horizontal 
axis  at  a  point  a  few  feet  beyond  the  exhauster  and  two  sampling 
tubes  inserted,  one  extending  to  the  middle  of  the  main  and  the 
other  projecting  through  the  wall  only  about  an  inch.  Four 
tests  were  made  and  in  each  case  the  suspended  tar  caught  in  the 
sampling  tube  near  the  edge  of  the  main  was  more  than  twice  as 
great  as  that  found  in  the  tube  projecting  to  the  center. 

3.  Mean  Velocity  in  the  Cross-section  of  a  Gas  Main. — Threl- 
fall2  has  shown  that  it  is  necessary  to  investigate  the  distribution 
of  velocity  for  each  individual  case  as  it  arises,  but  that  in  general 
the  radius  of  the  circle  of  mean  velocity  is  about  0.775  of  the  ra- 
dius of  the  pipe.     In  one  case  it  was  as  high  as  0.9  of  the  radius  but 
in  no  case  did  it  sink  to  0.69  which  is  the  figure  quoted  for  water 
flowing  through  a  long  and  smooth  pipe.     The  radius  of  mean 
velocity  did  not  change  with  varying  speed  of  gas  flowing  through 
the  pipe  within  the  ranges  of  600  ft.  and  3600  ft.  per  minute, 
which  marked  the  limit  of  the  experiments.     Threlfall's  experi- 
ments were  on  pipes  varying  from  6  to  36  in.  in  diameter. 

4.  Influence  of  Bends  in  a  Main. — If  gas  flowing  through  a 
straight  main  comes  to  a  bend  there  will  be  a  change  in  the  rela- 
tive velocities  of  the  particles  of  the  gas  throughout  the  cross- 
section.     The  kinetic  energy  of  a  body  is  represented  by  the 
expression  l/2mv2  where  m  represents  the  mass  of  a  body  and  v  its 
velocity.     It  is  evident  therefore  that  the  particles  with  the 
greatest  mass  and  the  greatest  velocity  will  be  projected  beyond 

1  Proc.  Mich.  Gas.  Ass.,  1906. 
2Proc.  Inst.  Mech.  Eng.,  1904,  1,  245. 


140  GAS  AND  FUEL  ANALYSIS 

their  companions.  The  point  of  maximum  velocity  will  shift 
from  the  center  to  a  point  nearer  the  opposing  wall  and  will  then 
slowly  return  to  its  normal  position  with  a  spiral  movement. 
Solid  particles  on  account  of  their  greater  mass  may  strike  the 
opposing  wall  and  if  they  or  the  wall  are  sticky  may  adhere  there 
and  build  up  deposits. 

It  will  be  evident,  from  what  has  preceded,  that  it  will  not  be 
possible  to  find  a  single  point  in  a  gas  main  from  which  it  is  pos- 
sible to  draw  a  fair  sample  of  gas  for  the  determination  of  sus- 
pended solids.  If  a  sample  can  only  be  taken  at  a  single  point, 
the  termination  of  the  sampling  tube  should  be  at  about  the  point 
of  mean  velocity,  as  explained  in  the  preceding  section.  In  im- 
portant tests  it  is  advisable  to  draw  a  number  of  samples  from 
various  points  in  the  cross-section  of  the  main.  A  tube  with  nu- 
merous perforations  along  its  length  is  useless  for  this  work.  Sep- 
arate tubes  should  be  used  each  with  its  own  filter  and  aspi- 
rator as  explained  in  Chapter  I. 

5.  Velocity  of  Gas  in  a  Sampling  Tube. — The  rate  of  flow 
through  the  sampling  tube  has  a  ma- 
terial effect  on  the  accuracy  of  sam-  * 

pling  as  has  also  the  inclination  of  the      

sampling  tube  to  the  gas  stream.     It     __>  N.       B 

is  evident  that  if  -a  sampling  tube  is       * 

inserted  at  A  of  Fig.  35  at  right  angles 
to  the  flow  of  gas,  even  assuming  that 
the  solid  particles  are  uniformly  dis- 
tributed, the  result  will  be  incorrect        FlG  35>_Diagram  show. 
for  the  heavy  particles  will  tend  to  be     ing  method  of  inserting  sam- 
carried  past  the  open  end  of  the  tube     pling  tube  in  gas  main, 
and  not  drawn  into  it.     The  suspended 

solids  will  be  reported  low  even  if  the  speed  of  gas  within  the  sam- 
pling tube  is  as  high  or  even  higher  than  that  in  the  main.  If,  on 
the  other  hand,  the  opening  of  the  sampling  tube  faces  the 
approaching  stream  of  solid  particles  as  at  B,  on  the  same  assump- 
tion of  uniform  distribution  of  particles,  the  result  may  be  cor- 
rect, or  it  may  be  high  or  low.  If  the  speed  of  the  gas  in  the  sam- 
pling tube  is  the  same  as  that  in  the  main  the  result  should  theo- 
retically be  correct.  The  whole  column  of  gas  opposite  the  open- 
ing of  the  tube  should  enter  without  distortion.  If,  however,  the 


ESTIMATION  OF  SUSPENDED  PARTICLES  IN  GAS       141 

velocity  in  the  sampling  tube  is  lower  than  that  in  the  main 
the  column  of  gas  approaching  the  opening  will  be  disturbed  and 
part  of  it  will  be  forced  aside.  'The  solid  particles  will  on  account 
of  their  momentum  not  be  pushed  aside  so  readily  and  will  there- 
fore enter  the  tube  in  unduly  great  amount,  giving  a  high  result. 
If  the  velocity  of  the  gas  in  the  sampling  tube  is  greater  than  that 
in  the  main  there  will  again  be  a  disturbance  in  the  approaching 
column  of  gas.  A  column  of  gas  larger  than  the  opening  of  the 
tube  will  be  sucked  in,  but  the  solid  particles  in  the  outer  shell 
of  gas  thus  sucked  in  will  not  be  diverted  from  their  course  and 
will  pass  by  the  opening  of  the  tube,  giving  a  low  result.  Brady1 
states  that  in  sampling  blast-furnace  gas  an  error  of  more  than 
44  per  cent,  was  caused  when  the  sampling  speed  was  dropped  to 
half  that  in  the  main.  It  is  thus  evident  that  the  speed  with 
which  gas  enters  the  sampling  tube  must  be  carefully  controlled. 
The  velocity  of  the  gas  must  however  be  reduced  before  it 
passes  through  the  filtering  medium  or  the  finely  divided  particles 
will  not  be  taken  out.  The  usual  sampling  tube  has  therefore  a 
relatively  small  aperture.  Care  must  be  taken  that  the  aperture 
is  not  so  small  that  it  will  become  clogged,  which  readily  happens 
when  tarry  matters  are  present.  Each  case  must  be  studied 
independently. 

6.  The  Filtering  Medium. — Where  conditions  permit,  filter 
paper  discs  or  shells  make  satisfactory  filtering  media.  The 
Brady  gas  filter  for  dust  in  blast-furnace  gas  is  described  in  the 
article  referred  to  in  the  preceding  section.  A  filter  using  a  disc 
of  filter  paper  as  developed  by  Mr.  W.  S.  Blauvelt2  of  the  Semet- 
Solvay  Company  has  been  used  by  the  author  with  good  results. 
Various  commercial  filters  of  this  type  are  now  on  the  market. 

When  large  amounts  of  tar  are  present  a  weighed  tube  filled 
with  a  fibrous  •material  may  with  advantage  be  inserted  ahead  of 
the  filter  paper.  The  filtering  materials  to  be  inserted  in  the  sam- 
pling tube  will  vary  with  conditions.  If  the  temperature  is  high, 
sand  or  ignited  asbestos  is  suitable.  Ignited  asbestos  is  usually  to 
be  preferred  since  on  account  of  its  fibrous  nature  it  makes  a  more 
efficient  and  a  lighter  filter.  This  last  consideration  is  of  impor- 
tance since  the  suspended  solids  collected  frequently  weigh  only 
a  few  milligrams  and  it  conduces  to  accuracy  to  have  the  increase 

1  Jour.  Ind  and  Eng.  Chem.,  3,  662  (1911). 
zProc.  Am.  Gas.  Inst.,  4,  795  (1909). 


142 


GAS  AND  FUEL  ANALYSIS 


in  weight  of  the  filter  relative  to  its  initial  weight  as  large  as  may 
be.  The  tubes  may  be  of  glass,  porcelain  or  quartz  protected  if 
desirable  by  an  iron  j  acket.  The  tubes  after  filling  and  before  use 
should  be  placed  in  an  air  bath  heated  to  the  temperature  to  which 
they  are  to  be  exposed  later  and  dry  air  should  be  drawn  through 
them  until  they  are  constant  in  weight.  They  should  then  be 
cooled  in  dry  air,  weighed,  carefully  stoppered  and  if  possible 
kept  in  a  dessicator  until  used.  The  asbestos  for  this  purpose 
should  not  be  soft  enough  to  pack  readily  and  choke  the  tube. 
The  fine  washed  asbestos  used  for  analytical  work  is  not  so  good  for 
this  purpose  as  a  cruder  sort.  Sometimes  when  much  tar  is 
present  it  is  advantageous  to  procure  the 
crude  asbestos  rock  and  merely  crush  it 
coarsely  in  an  iron  mortar. 

7.  Estimation  of  Suspended  Tar  and 
Water. — The  amount  of  suspended  matters 
caught  by  a  filter  paper  may  be  estimated 
either  by  color  or,  if  sufficient  in  amount, 
may  be  determined  by  weight.  A  second 
weight  after  drying  at  105°  C.  for  an  hour 
will  give  by  difference  the  moisture  and 
other  volatile  matter,  while  the  weight  after 
ignition  will  give  the  mineral  matter,  cor- 
rection being  made  if  necessary  for  the 
change  in  composition  due  to  ignition.  The 
Steere  Engineering  Company  manufactures 
a  convenient  filtering  device  which  they 
name  a  tar  camera  and  which  is  illustrated 
in  Fig.  36.  They  furnish  with  it  a  colori- 
metric  chart  from  which  the  amount  of  sus- 
FIG.  36  —Tar  camera  pen(jed  tar  may  be  determined  directly  by 

for  colorimetxic  tar  de-    h  J 

termination.  Comparison  of  colors. 

Where  asbestos  filters  have  been  used  a 

similiar  procedure  may  be  followed  provided  the  asbestos  has 
been  ignited  before  use.  In  drying  the  tube  however  it  is  not 
sufficient  to  heat  it  externally.  Dry  air  must  be  drawn  through 
until  it  comes  to  constant  weight.  The  water  will  be  driven  off 
and  also  approximately  25  per  cent,  of  the  weight  of  the  tar. 
The  non-volatile  tar  remaining  may  afterward  be  extracted  with 


ESTIMATION  OF  SUSPENDED  PARTICLES  IN  GAS        143 

chloroform  or  carbon  bisulphide,  and  this  figure  increased  by  one- 
third  will  give  a  rough  estimate  of  the  amount  of  tar  present. 
It  is  not  possible  to  determine  accurately  the  amounts  of  water 
and  suspended  tar  since  it  is  not  feasible  to  determine  how  much 
of  the  material  volatilized  is  tar  and  how  much  is  water. 

8.  Electrical  Precipitation  of  Suspended  Particles. — Where 
the  expense  warrants  the  installation  of  the  process,  the  method  of 
electrical  precipitation  as  developed  on  the  large  scale  so  success- 
fully by  Cottrell1  may  be  applied.  The  equipment  consists  of  a 
small  step-up  auto  transformer  capable  of  giving  15,000-30,000 
volts,  a  rectifier  for  this  high-tension  alternating  current  and  a 
precipitating  vessel  which  may  be  made  of  an  iron  pipe  with  an 
insulated  electrode  in  the  center.  An  exhauster  for  aspirating 
the  gas  and  a  meter  for  measuring  it  must  also  be  provided. 
This  apparatus  will  quantitatively  precipitate  all  suspended 
solid  and  liquid  bodies  including  tar  and  operates  on  such  large 
volumes  that  the  precipitated  materials  can  readily  be  examined. 

1  Jour.  hid.  and  Eng.  Chem.,  3,  542,  (1911). 


CHAPTER  X 
CHIMNEY  GASES 

1.  Introduction. — A  knowledge  of  the  chemical  composition 
of  the  gases  escaping  from  a  chimney  aids  much  in  controlling 
the  efficiency  of  the  furnace.     It  makes  very  little  difference 
whether  the  fuel  is  burned  to  raise  steam  or  to  melt  steel  and  it  is 
of  equally  small  importance  whether  the  fuel  burned  be  solid  or 
liquid.     The  only  assumption  is  that  it  is  desirable  to  burn  the 
fuel  as  completely  as  possible  without  the  introduction  of  any 
unnecessary  excess  of  air.     When  gaseous  fuels  are  burned  the 
same  general  principles  apply  but  there  is  somewhat  greater 
complication  in  calculation.     This  chapter  therefore  limits  itself 
to  a  study  of  the  gases  arising  from  complete  combustion  of 
solid  or  liquid  fuels.     Let  us  see  how  much  light  a  knowledge  of 
the  composition  of  the  gas  can  throw  on  the  operation  of  the 
furnace. 

2.  Sampling. — Samples  should  be  drawn  from  a  point  as  near 
to  the  fire  as  possible,  while  still  allowing  time  for  complete 
combustion.     Irregular  streams  of  unburned  gases  may  arise  from 
a  bituminous  coal  fire  with  adjacent  streams  of  almost  unchanged 
air.     Kreisinger,    Augustine,    and    Ovitz1  have    shown   that  if 
samples  are  taken  a  short  distance  beyond  the  firebox  of  a  fur- 
nace such  as  is  used  in  boiler  plants  the  percentage  of  carbon 
dioxide  may  vary  from  0.8  to  15.6  per  cent,  in  two  samples  taken 
simultaneously  and  only  sixteen  inches  apart.     When  composite 
samples  obtained  over  a  period  of  eight  minutes  were  drawn  from 
points  only  eleven  inches  apart  and  four  feet  from  the  combustion 
chamber  there  was  still  a  difference  of  1.0  per  cent,  in  the  carbon 
dioxide  of  the  two  samples.     If,  however,  the  investigator  goes  a 
long  distance  from  the  point  of  combustion  in  an  effort  to  obtain 
a  fair  sample,  he  runs  the  danger  of  finding  his  gases  diluted  by  air 
pulled  through  leaks  in  the  setting.     The  very  greatest  care  must 
therefore  be  exercised  in  sampling  chimney  gases. 

1  Bui.  135  Bureau  of  Mines.     Combustion  of  Coal  and  Design  of  Furnaces. 

144 


CHIMNEY  GASES  145 

3.  Formation  of  Carbon  Dioxide. — Air  is  composed  of  prac- 
tically 21  volumes  of  oxygen  and  79  volumes  of  nitrogen  and  other 
inert  gases.     When  oxygen  unites  with  carbon  there  is  formed 
carbon  dioxide  which  is  stable  unless  it  comes  into  intimate  con- 
tact with  carbon  or  other  reducing  agent  at  a  high  temperature. 
Chemically  the  result  is  expressed  as  follows: 

C  +  02  =  C02. 

The  expression  means  not  only  that  carbon  dioxide  is  formed 
by  the  union  of  carbon  and  oxygen,  but  also  indicates  that  one 
volume  of  carbon  dioxide  is  formed  from  one  volume  of  oxygen  and 
that  the  volume  of  the  smoke  gases  after  cooling  is  the  same  as  that 
of  the  air  which  was  used.  This  follows  from  the  law  of  Gay 
Lussac  which  states  that  a  molecule  of  one  gas  occupies  the  same 
volume  as  that  of  any  other  gas  under  like  conditions.  The 
simplicity  of  this  volume  relation  makes  it  extremely  desirable 
to  work  with  volumes  instead  of  weights  in  problems  where  gases 
are  involved. 

Since  one  volume  of  oxygen  forms  one  volume  of  carbon  dioxide 
it  follows  that  the  theoretically  best  composition  of  the  chimney 
gases  from  the  combustion  of  carbon  would  be  21  per  cent.  CO2 
and  79  per  cent.  N2.  This  is  unattainable  in  practice  because  the 
strong  reducing  action  of  the  glowing  carbon  on  the  carbon 
dioxide  will  cause  formation  of  carbon  monoxide  (CO)  which  will 
not  be  again  oxidized  unless  it  is  brought  in  contact  with  free 
oxygen  while  still  at  a  high  temperature.  An  excess  of  oxygen  is 
in  practice  necessary  to  ensure  this.  It  follows  from  the  fact  that 
the  volume  of  the  carbon  dioxide  is  the  same  as  that  of  the  oxygen 
which  formed  it,  that  all  chimney  gases  resulting  from  the  com- 
bustion of  pure  carbon  to  carbon  dioxide  will  contain  21  per  cent, 
of  CO2+O2  and  79  per  cent,  of  N2. 

4.  Effect  of  Hydrogen  of  Coal  on  Composition  of  Chimney 
Gases. — -The  simple  relation  stated  in  the  preceding  section  only 
holds  where  carbon  is  the  only  fuel  burned,  a  condition  which  is 
quite  closely  fulfilled  with  a  coke  fire  and  approximately  ful- 
filled when  anthracite  coal  is  the  fuel.     When  fuels  contain  not- 
able percentages  of  hydrogen,  as  does  bituminous  coal,  and  to  a 
greater  extent  petroleum  and  most  gaseous  fuels,  part  of  the 
oxygen  of  the  air  burns  to  water  which  escapes  from  the  furnace 
as  steam. 


146  GAS  AND  FUEL  ANALYSIS 

The  changes  which  air  undergoes  on  combustion  with  coal  may 
be  illustrated  as  follows : 

100  cu.  ft.  dry  entering  air  is  distributed: 
79  cu.  ft.  N2 
10  cu.  ft.  O2  to  combine  with  C 

9  cu.  ft.  O2  as  excess 

2  cu.  ft.  O2  to  combine  with  H  of  coal 

Products  of  combustion  from  100  cu.  ft.  dry  air  after  cooling  tc 
initial  temperature. 

79  cu.  ft.  N2 
10  cu.  ft.  CO2 

9  cu.  ft.  O2 

4  cu.  ft.  H2O 

102  cu.  ft.  total  volume 

The  water  in  this  illustration  will  have  a  volume  of  4.0  cu.  ft.  if 
it  remains  in  the  state  of  vapor  after  cooling  to  the  initial  tem- 
perature of  the  air  before  combustion. 

If  this  combustion  had  taken  place  in  the  bomb  calorimeter 
where,  instead  of  dry  air,  oxygen  saturated  with  moisture  is 
used,  the  4.0  cu.  ft.  of  water  would  have  condensed  to  liquid 
when  the  products  had  cooled  to  their  initial  temperature.  If 
combustion  gases  taken  from  the  bomb  are  analyzed  in  the 
usual  way  in  a  burette  filled  with  water  so  that  the  gases  always 
remain  saturated  with  water  vapor,  no  account  whatever  would 
be  taken  of  the  water  vapors  and  the  analysis  reported  would  be 
the  same  as  if  the  gas  volume  had  been : 

79  cu.  ft.  N2  80 . 6  per  cent. 

10  cu.  ft.  CO2  10 . 2  per  cent. 

9cu.  ft.  O2  9. 2  per  cent. 

98  cu.  ft.  100 . 0  per  cent. 

Let  us  now  work  backwards  from  this  gas  analysis  which  may 
be  assumed  to  represent  the  composition  reported  for  a  stack 
gas.  When  the  gas  sample  was  being  drawn  part  of  the  steam 
formed  may  have  condensed.  If  the  gas  sample  was  stored  over 
water  it  certainly  became  fully  saturated  with  water  vapor  so 
that  its  volume  became  entirely  independent  of  the  amount  of 
steam  which  it  contained  in  the  chimney.  The  resulting  gas 


CHIMNEY  GASES  147 

composition  would  then  be  the  same  as  if  the  combustion  had 
taken  place  in  the  bomb  calorimeter.  The  calculation  would  be 
as  follows:  100  cu.  ft.  of  air  contained  79  cu.  ft.  of  nitrogen 
which  is  now  80.6  per  cent,  of  the  chimney  gas,  therefore  the 

79 
volume  of  the  gas  is  gQ~^  =  0.98,  or  98  per  cent,  of  the  initial 

volume  of  entering  air  measured  under  the  same  conditions  of 
temperature  and  pressure.  It  follows  that  2.0  of  the  21  volumes 
of  oxygen  have  combined  with  hydrogen  to  form  water. 

The  volume  of  the  water  formed,  so  long  as  it  remains  in  the 
vapor  form,  will  be  twice  that  of  the  oxygen  from  which  it  was 
formed  as  shown  by  the  equation. 

2H2  +  02  =  2H20. 

The  hydrogen  in  this  case  is  contained  in  the  coal  and  is  con- 
sidered as  a  solid  just  as  the  carbon  is.  In  the  case  of  gaseous 
fuels  the  problem  is  a  little  more  complicated  and  is  treated 
under  Pro'ducer  Gas. 

5.  Carbon  Monoxide  and  Products  of  Incomplete  Combus- 
tion.— The  presence  of  carbon  monoxide,  hydrogen  or  hydro- 
carbons is  a  sign  of  incomplete  combustion  and  represents  loss 
of  heat  which  would  have  been  liberated  in  the  furnace  had 
combustion  been  complete. 

Heating  value  1  Ib.  C  to  CO2 14,600  B.t.u. 

1  Ib.  C  to  CO 4,450  B.t.u. 

Since  carbon  burning  to  CO  only  evolves  30  per  cent,  of  the  heat 
obtainable  by  complete  combustion  it  is  evidently  uneconomical 
to  allow  more  than  small  amounts  of  this  gas  to  appear  in  chimney 
gases. 

It  is  frequently  stated  that  carbon  monoxide  is  formed  when 
carbon  burns  with  an  insufficient  supply  of  air.  This  is  only  a 
partial  truth  for  with  a  bed  of  coals  at  a  dull  red  heat  it  is  difficult 
to  form  carbon  monoxide  no  matter  how  much  the  air  supply  is 
limited.  If  the  free  oxygen  in  the  chimney  gases  is  below  3 
per  cent,  it  will  be  entirely  normal  to  find  products  of  incomplete 
combustion.  The  presence  of  carbon  monoxide  and  other  in- 
completely burned  gases  is  abnormal  when  associated  with  much 
more  than  3  per  cent,  free  oxygen.  It  indicates  either  a  faulty 
design  of  the  furnace  or  carelessness  on  the  part  of  the  fireman. 


148  GAS  AND  FUEL  ANALYSIS 

Furnaces  intended  for  coal  high  in  volatile  matter  must  have 
roomy  combustion  chambers  so  that  the  streams  of  gas  given  off 
by  the  coal  may  have  time  to  mix  with  air  and  burn  before  they 
become  chilled  by  contact  with  cold  surfaces.  Furnaces  designed 
for  anthracite  coal  do  not  have  such  large  combustion  chambers 
and  hence  do  not  give  good  results  with  bituminous  coal. 

As  mentioned  in  Chapter  III,  the  estimation  of  carbon  monox- 
ide presents  some  difficulties  and  the  careless  analyst  may  readily 
report  a  fraction  of  a  per  cent,  of  carbon  monoxide  when  none  is 
there.  On  the  other  hand,  the  natural  tendency  is  to  fail  to  find 
hydrogen  when  it  is  present  in  only  small  amounts. 

The  presence  of  soot  in  chimney  gases  is  not  necessarily  an  in- 
dication that  measureable  amounts  of  unburned  gases  are  present 
for  the  particles  of  tar  and  carbon  formed  by  the  destructive 
distillation  of  the  coal  burn  much  more  slowly  than  do  the 
gases  and  also  have  higher  ignition  temperatures  and  so  are  more 
likely  to  escape  combustion. 

6.  Volume  of  Air  and  of  Chimney  Gases. — The  volume  of  the 
air  used  in  combustion  per  pound  of  carbon  and  the  volume  of  the 
chimney  gases  may  be  calculated  from  the  gas  analysis.  The 
method  is  based  on  the  assumption  that  the  nitrogen  of  the  air 
passes  through  the  furnace  unchanged  in  volume,  and  that  all  of 
the  nitrogen  of  the  chimney  gases  is  derived  from  the  air.  This 
assumption  is  practically  correct,  the  small  amount  of  nitrogen 
derived  from  the  coal  introducing  only  a  negligible  error. 

It  is  necessary  also  to  have  some  factor  to  connect  the  weight 
of  carbon  burned  with  the  volume  of  the  chimney  gases.  One 
pound  of  carbon  burning  to  CO2  requires  32.1  cu.  ft.  of  oxygen 
measured  wet  at  60°  F.,  and  30  in.  barometric  pressure  and 
yields  32.1  cu.  ft.  carbon  dioxide.  If  the  air  were  perfectly  dry 
only  31.4  cu.  ft.  would  be  needed  per  pound  of  carbon  and  the 
volume  of  carbon  dioxide  would  be  31.4  cu.  ft. 

Let  us  assume  the  following  gas  analysis : 

CO2 8.5  per  cent. 

O2 10.8  per  cent. 

N»  - 80 . 7  per  cent. 

It  was  shown  in  §  3  that  the  increase  in  the  percentage  of  the 
nitrogen  over  79  was  due  to  the  condensation  of  steam  formed  by 


CHIMNEY  GASES  149 

the  union  of  hydrogen  of  the  coal  with  oxygen  of  the  air.     The 
volume  of  these  gases  referred  to  100  of  air  may  be  obtained  by 

79 
multiplying  them  by  the  factor  5^  =  0.979. 

oU.  i 

8.5X0.979=  8.3CO2 
10.8X0.979=  10.6  O2 
80.7X0.979=  79.0  N2 

97.9 
O2  which  has  disappeared  as  steam      2 . 1  forming  4 . 2  steam. 

100.0 

The  volume  of  air  used  per  pound  of  carbon  may  now  be  ob- 
tained. 

To  burn  1  Ib.  carbon  =32. 1  cu.  ft.  moist  O2  forming  32. 1  cu. 

ft.  CO2 
32.1X10.6 
Oxygen  in  excess         5-0 =41 . 1 

o.  o 

,  A         32.1X2.1 

Oxygen  forming  steam ^—5 =  8.1 

o .  o 

Total  oxygen  per  pound  carbon,         81 . 3  cu.  ft. 

79 
Accompanied  by  ^  X  81 . 3  =  305 . 5  cu.  f t.  Nt 

Corresponding  to  386 . 8  cu.  ft.  air. 

The  excess  of  air  may  be  determined  from  the  ratio 

Oxygen  used     ^32. 1+41. 1+8. 1  =  81.3 
Oxygen  required          32.1+8.1  40.2    ' 

The  volume  of  the  chimney  gases  is  obtained  directly  from  the 
above,  it  being  remembered  that  the  volume  of  the  C02  is  the 
same  as  that  of  the  O2  forming  it  and  that  the  volume  of  the  steam 
(assumed  to  be  cooled  to  standard  temperature  without  condensa- 
tion) is  twice  the  volume  of  the  oxygen  forming  it. 

Volume  of  chimney  gases  from  1  Ib.  carbon  in  the  above 
example : 

CO2 32. 1  cu.  ft. 

H2O  vapor  2X8.1 16.2  cu.  ft. 

O2 41 . 1  cu.  ft. 

N2 t 305.5  cu.  ft. 

Total  chimney  gases  394. 9  cu.  ft. 


150  GAS  AND  FUEL  ANALYSIS 

7.  Loss  of  Heat  in  Chimney  Gases. — The  bomb  calorimeter 
gives  the  heating  value  of  coal  with  100  per  cent,  efficiency.  In 
this  instrument  the  gases  are  cooled  to  practically  the  same 
temperature  as  before  ignition  and  all  water  formed  in  combus- 
tion is  condensed  to  liquid  water.  The  calorimeter  makes  no 
distinction  between  water  present  as  moisture  in  the  coal  or  as 
combined  water  in  the  coal,  and  the  water  formed  by  combustion 
of  the  available  hydrogen  or  hydrocarbons.  In  calculating  the 
loss  of  heat  in  chimney  gases  the  clearest  procedure  is  to  deter- 
mine what  would  have  been  the  state  of  the  products  of  combus- 
tion if  combustion  had  taken  place  in  a  bomb  calorimeter,  and 
then  calculate  the  losses  caused  by  the  higher  temperature  of 
the  gases  and  the  presence  of  water  in  the  state  of  vapor  rather 
than  as  liquid. 

The  heat  carried  away  by  these  gases  may  be  determined  by 
multiplying  their  volume  by  the  rise  in  temperature  and  by  their 
specific  heat.  It  was  first  shown  in  1883  by  Mallard  and  Le- 
Chatelier  that  the  specific  heats  of  gases  are  not  constant  but  in- 
crease with  rising  temperature.  Engineers  have  been  slow  to 
adopt  these  variable  specific  heats  but  there  can  be  no  question 
as  to  their  general  correctness.  The  mean  specific  heats  ex- 
pressed in  British  thermal  units  per  cubic  foot  and  per  pound  at 
constant  pressure  have  been  calculated  by  the  author  from  the 
data  of  Holborn  and  Henning1  and  are  given  in  Tables  X  and 
XI  of  the  Appendix.  It  will  be  noted  that  the  specific  heats  of 
oxygen,  nitrogen  and  all  permanent  gases  are  the  same  per  cubic 
foot,  an  agreement  which  holds  true  only  for  specific  heats  by 
volume  and  not  for  those  for  which  the  unit  basis  is  weight. 

The  loss  of  heat  per  pound  of  carbon  in  the  particular  case 
given  above  will  be  calculated  as  follows,  a  temperature  of  600° 
F.  for  the  escaping  gases  being  assumed : 

Temperature  through  which  gases  are  heated  600  —  60  =  540. 
Use  mean  specific  heats  from  Table  X  corresponding  to  600°  F. 

Heat  lost  in  CO2,  32 . 1 X 0 . 0253  X  540  =  439  B.t.u. 

Heat  lost  in  steam,        16 . 2  X  0 . 0221 X  540  =   193 

Heat  lost  in  oxygen,      41  1  j  346<6xo. 0177X540  =  3310  B.t.u. 

Heat  lost  in  nitrogen,  305 . 5  J  

3942 

1  Annalen  der  Physik,  23,  809  (1907). 


CHIMNEY  GASES  151 

It  is  necessary  to  know  the  percentage  of  carbon  in  the  coal 
before  this  loss  of  heat  per  pound  carbon  can  be  calculated  to 
the  desired  basis  of  loss  per  pound  of  coal. 
The  loss  of  heat  per  pound  of  dry  coal  = 

Loss  per  pound  carbon  X  per  cent,  carbon  in  dry  coal 

100 

Moisture  present  in  the  coal  when  placed  on  the  fire  will  be 
vaporized,  and,  in  case  combustion  is  complete,  will  escape  from 
the  stack  as  steam.  It  is  immaterial  whether  or  not  it  underwent 
decomposition  in  the  fire,  only  the  initial  and  final  states  being 
important.  The  amount  of  water  thus  vaporized  calculated 
from  the  analysis  of  the  coal  is  reported  in  pounds  and  is  most 
conveniently  kept  in  that  form  throughout  the  calculation.  The 
mean  specific  heats  by  weight  at  constant  pressure  are  given  in 
Table  XI  of  the  Appendix.  Moisture  present  in  the  air  intro- 
duced into  the  firebox  will  be  heated  from  room  temperature  to 
that  of  the  escaping  gases.  Its  amount  may  be  determined  from 
observations  with  a  wet  and  dry  bulb  thermometer  from  which 
the  percentage  humidity  may  be  calculated  as  described  in  §  16  of 
Chapter  VII.  The  volume  of  water  vapor  per  cubic  foot  of  air 
for  various  temperatures  is  given  in  Table  XII  of  the  Appendix. 

There  is  also  steam  in  the  stack  gases  which  is  derived  from 
the  union  of  the  hydrogen  and  oxygen  of  the  coal  with  each 
other.  It  is  sufficiently  accurate  to  assume  that  all  of  the  oxy- 
gen of  the  coal  unites  with  the  hydrogen  of  the  coal  to  form  water, 
that  the  excess  or  available  hydrogen  unites  with  the  oxygen  of 
the  air  td  form  water  and  that  all  of  the  carbon  of  the  coal 
unites  with  the  oxygen  of  the  air  to  form  carbon  dioxide.  The 
volume  of  steam  due  to  this  union  of  the  hydrogen  and  oxygen 
of  the  coal  with  each  other  can  only  be  accurately  calculated  from 
an  ultimate  analysis.  Fortunately  its  amount  is  small  and  fairly 
constant  for  a  given  type  of  coal.  The  weight  of  water  so  formed, 
sometimes  called  " combined  water,"  may  be  taken  as: 

2.5  per  cent,  for  anthracite  coals. 
6.0  per  cent,  for  Eastern  bituminous  coals. 
10.0  per  cent,  for  bituminous  coals  of  the  Western  or  Illinois  type. 

These  figures  may  for  this  purpose  be  added  to  the  percentage 
of  moisture  in  the  coal. 


152  GAS  AND  FUEL  ANALYSIS 

There  are  also  changes  in  the  ash  of  the  coal  which  may  in- 
volve absorption  of  oxygen  or  liberation  of  SO2  or  CO2  but  they 
are  negligible  in  a  calculation  of  this  sort. 

PROBLEM  ILLUSTRATING  CALCULATION  OF  LOSS  OF  HEAT  IN 
CHIMNEY  GASES 

~    .  Average  composition  of 

Data  Coal  as  charged 

chimney  gases 

Moisture 9.3  per  cent. 

Volatile  matter. .  31.7  CO2 9. 6  per  cent. 

Fixed  carbon 53.7  O2 9.8 

Ash 5.3  N, 80.6 

100.0  100.0 

B.t.u.  per  Ib 12,456  Temp,  escaping  gases. .  720°  F. 

Per  cent,  total  carbon. .     71 . 6  Temp,  inlet  air 70°  F. 

Relative  humidity 75  per  cent. 

Distribution  of  air  entering  furnace. 

Factor  to  correct  for  change  of  volume  caused  by  formation  of  water  in 

79 
combustion  o7r~g  =  0 . 98 

9 . 6  X  0 . 98  =     9 . 4  O2  f or  burning  carbon 
9.8X0.98=     9.6  O2  in  excess 
80.6X0.98=  79.0  N2 


98.0 
2 . 0  O2  for  burning  hydrogen 

100.0 

Volume  gases  from  1  Ib.  carbon. 

1  Ib.  carbon  produces  31 .4  cu.  ft.  dry  CO2. 
Factor  ^^=3. 34 

9.4X3.34=  31.4cu.  ffc.  CO2 
4.0X3.34=   13.4cu.  ft.  H2O  vapor 
9.6X3.34=  32.7cu.  ft.  O2 
79. 0X3. 34  =  263. 8  cu.  ft.  N2 

Volume  dry  air  required  for  combustion  100X3.34  =  334  cu.  ft. 
Moisture  in  air  for  combustion  assumed  as  75  per  cent,  of  saturation 
at  70°  F. 

0.75X0.026=0.019  cu.  ft.  per  cu.  ft.  air 
334 . 00  X 0 . 019  =  6 . 35    cu.  ft.  for  1  Ib.  carbon 


CHIMNEY  GASES  153 

Losses  due  to  sensible  heat  of  gases. 

Gases  heated  from  70°  -  720°  F. 

Loss  in  CO2  =  3  1.4X650X0.  0257-  525  B.t.u. 

Loss  in  H2O  (sensible  heat  only) 

vapor  from  entering  air  ....................     6.35  cu.  ft. 

formed  from  available  H  of  coal  .............    13.4    cu.  ft. 

moisture    (9.3)    and    combined  water   (6.0) 

of  coal  =  0  .  153  Ib.  per  Ib.  coal  • 


carbon  with  0  .  0476  cu.  ft.  per 

Ib.  (Table  IX,  Appendix)  ...............     4.5    cu.  ft. 

Total  water  vapor  .........................   24.  25  cu.  ft. 

Heat  lost  =  24  .  25  X  650  X  0  .  0221  =  347  B.t.u. 

Loss  in  O2and  N2  32.7+263.8  =  296.5X650X0.0177=  3410  B.t.u. 

Total  B.t.u.  lost  in  sensible  heat  per  Ib.  carbon  ................  4282 

Total  B.t.u.  lost  in  sensible  heat  per  Ib.  coal  4285X0.716=         3065 

Losses  due  to  latent  heat  of  water. 

Moisture  in  coal  9.3  per  cent.  =0.093  Ib.  per  Ib.  coal 

Combined  water  in  coal  6.0  per  cent.  =0.060  Ib.  per  Ib.  coal 

Water  formed  by  combustion  of  available  H  of  coal 

forming  13  .  4  cu.  ft.  H2O  vapor  with  0  .  0476  Ib.  per 

cu.  f  t.  =  13  .  4  XO  .  0476  =  0  .  638  Ib.  per  Ib.  carbon  = 

0.638X0.716  =0.4571b.  per  Ib.  coal 

Total  water  which  would  have  condensed  had  com- 

bustion taken  place  in  bomb  calorimeter  0.  610  Ib.  per  Ib.  coal 

Latent  heat  of  vaporization  0  .  610  X  1067  =  651  B.t.u. 

Total  heat  losses  per  Ib.  coal  burned. 

Sensible  heat  of  gases  =  3065  B.t.u. 
Latent  heat  of  water  =  651  B.t.u. 

Total  heat  lost  =3716  B.t.u. 

O*7  "I  f* 

Per  cent,  heat  lost  v>456  =  2^  •  8  Per  cent* 

8.  Interpretation  of  Analysis  of  Chimney  Gases.  —  An  analysis 
is  of  no  value  unless  the  sample  is  representative.  Some  of  the 
difficulties  in  sampling  are  mentioned  in  Section  2.  If  the  sam- 
pling and  analysis  have  been  properly  performed  the  conclusions 


154  GAS  AND  FUEL  ANALYSIS 

to  be  drawn  from  the  preceding  paragraphs  may  be  summarized 
as  follows: 

Carbon  Dioxide. — The  higher  the  percentage  of  CO2  in  chimney 
gases  without  the  presence  of  CO  or  hydrocarbons,  the  more 
efficient  is  the  furnace.  When  the  fuel  is  coke  or  anthracite  coal 
the  sum  of  the  percentages  of  carbon  dioxide  and  oxygen  should 
be  between  20.5  and  20.8.  If  the  fuel  is  bituminous  coal  the  sum 
of  the  carbon  dioxide  and  oxygen  will  drop  to  19  per  cent,  and  if 
the  fuel  is  oil  or  gas  the  figure  will  be  still  smaller.  In  ordinary 
practice  the  percentage  of  carbon  dioxide  should  be  as  large  as 
the  oxygen,  and  with  well-equipped  and  operated  plants  the  pro- 
portion of  CO2  to  O2  should  be  as  high  as  2  to  1.  With  liquid  or 
gaseous  fuels  the  proportion  of  CO2  will  be  still  higher. 

The  CO2  as  reported  includes  a  small  amount  of  S02  from  the 
sulphur  of  the  coal,  which  does  not  usually  amount  to  more  than 
a  few  hundredths  of  a  per  cent. 

Oxygen. — When  solid  fuel  is  burned  on  an  ordinary  grate  it  is 
necessary  to  have  an  excess  of  air  to  insure  complete  combustion. 
This  excess  should  be  kept  as  small  as  possible. 

Carbon  Monoxide  and  Products  of  Incomplete  Combustion. — 
These  products  should  be  entirely  absent  from  chimney  gases. 
Their  presence  indicates  waste  of  fuel.  Unless  the  analytical 
work  is  carefully  done  as  much  as  0.2  per  cent.  CO  may  readily 
be  reported  through  error. 

Nitrogen. — Nitrogen  is  present  in  air  to  the  extent  of  79  per 
cent,  by  volume  and  will  be  present  in  at  least  that  percentage  in 
chimney  gases.  With  bituminous  coal  the  percentage  will  rise 
to  81  per  cent,  and  with  oil  or  gaseous  fuel  the  percentage  will 
be  higher.  The  percentage  of  nitrogen  can  only  fall  below  79 
per  cent,  through  the  introduction  of  some  gas  which  makes  the 
total  volume  of  the  chimney  gases  greater  than  that  of  the  air 
from  which  they  were  derived.  The  formation  of  carbon  mon- 
oxide will  affect  this  result  since  it  occupies  twice  as  much  space 
as  the  oxygen  from  which  it  was  derived.  The  amount  of  CO 
in  chimney  gases  is,  however,  too  small  to  exert  any  appreciable 
influence  of  this  sort. 

Loss  of  Heat  in  Chimney  Gases. — The  loss  of  heat  will  depend 
on  the  temperature  and  volume  of  the  gases.  The  volume  of  the 
gas  is  in  general  indicated  by  the  relative  percentage  of  carbon 


CHIMNEY  GASES  155 

dioxide  and  oxygen.  The  higher  the  per  cent,  of  oxygen  and  the 
lower  the  per  cent,  of  carbon  dioxide  the  greater  is  the  loss  of 
heat.  The  loss  will  vary  in  steam-boiler  practice  between  15 
and  45  per  cent.  With  smelting  furnaces  where  the  gases  escape 
at  high  temperatures  the  loss  may  be  much  higher. 


CHAPTER  XI 
PRODUCER  GAS 

1.  Formation  of  Producer  Gas. — Producer  gas  is  formed 
whenever  air  is  brought  into  contact  with  fuel  under  such  con- 
ditions that  carbon  monoxide  is  an  important  constituent  of  the 
products  resulting  from  their  combination .  The  formation  of  pro- 
ducer gas  is  frequently  said  to  be  due  to  incomplete  combustion, 
but  the  statement  is  only  a  half  truth,  for  a  limited  quantity  of 
air  supplied  to  a  fire  will  not  necessarily  produce  carbon  monox- 
ide. The  primary  product  formed  when  carbon  burns  in  air 
is  carbon  dioxide,  the  equation  being  written 

C+02  =  C02 

If  this  carbon  dioxide  comes  into  intimate  contact  with  glowing 
carbon,  it  unites  with  more  carbon  and  carbon  monoxide  is 
formed  according  to  the  equation 

C02+C<=*2CO. 

These  two  reactions  are  frequently  combined  into  one  and  the 
typical  reaction  of  the  gas  producer  is  usually  written 

2C+02  =  2CO. 

This  equation  shows  that  one  volume  of  oxygen  is  converted 
into  two  of  carbon  monoxide.  The  composition  of  the  resulting 
gas  may  be  shown  as  follows : 

f  2102  =42CO  =  34.7  per  cent.  CO. 
=  I  79N2  =  79N2  =65.3  per  cent.  N2. 

When  steam  is  introduced  in  the  bottom  of  the  producer  the 
reaction  desired  is: 

C+H2O  =  CO+H2. 
156 


PRODUCER  GAS 


157 


If  the  temperature  of  the  producer  is  low,  this  reaction  may 
proceed  in  part  as  follows: 

C+2H20  =  C02+2H2. 

If  bituminous  coal  is  placed  in  the  producer  there  will  also  be 
products  of  destructive  distillation  including  hydrocarbons  both 
saturated  and  unsaturated,  hydrogen  and  carbon  monoxide. 

The  largest  single  constituent  of  producer  gas  is  nitrogen,  which 
will  not  often  fall  below  50  per  cent.  Carbon  monoxide  and 
hydrogen  rank  next  in  percentage.  The  hydrocarbons  are 
practically  always  under  5  and  are  usually  less  than  3  per 
cent.  Carbon  dioxide  should  be  low.  It  is,  however,  frequently 
as  high  as  10  per  cent. 

The  following  are  some  analyses  of  producer  gas.1 

TYPICAL  ANALYSES  OF  UP-DRAFT  PRESSURE-PRODUCER  GAS 
(Per  cent,  by  volume) 


From 
Bituminous  Coal 

From 
Lignite 

From 
Peat 

Carbon  dioxide  (CO2)  

9.84 

10.55 

12.40 

Oxvcen  (Q<>) 

.04 

0.16 

0.00 

Ethylene  (C2H4) 

.18 

0.17 

0.04 

Carbon  Monoxide  (CO) 

18  28 

18  72 

21.00 

Hydrogen  (Ha)            

12.90 

13.74 

18.50 

Methane  (CH4) 

3.12 

3.44 

2.20 

Nitrogen  (N2)  

55.64 

53.22 

45.50 

TYPICAL  ANALYSES  OF  DOWN-DRAFT  PRODUCER  GAS 
(Per  cent,  by  volume) 


From 
Bituminous  Coal 

From 
Lignite 

From 
Peat 

Carbon  dioxide  (CO2)  

6.22 

11.87 

10.94 

Oxygen  (O2)         

0.13 

0.01 

0.41 

Ethylene  (C2H4)               

0.01 

0.00 

0.06 

Carbon  monoxide  (CO)  
Hvdrocen  (H») 

21.05 
12  01 

16.01 
14.76 

16.91 
10.19 

Methane  (CH4)  
Nitrogen  (N2)  

0.49 
60.09 

0.98 
56.37 

0.66 
60.83 

1  From  Bulletin   13,  U.  S.  Bureau  of  Mines.     "Re'sume"  of  Producer-Gas 
Investigations  by  R.  H.  Fernald  and  C.  D.  Smith. 


158  GAS  AND  FUEL  ANALYSIS 

2.  Sampling    Producer    Gas. — The    quality    of    gas    yielded 
by  a  given  producer  may  change  quickly.     Soon  after  a  charge 
of  bituminous  coal  has  been  added,  the  amount  of  volatile  tarry 
vapors -and  of  gaseous  hydrocarbons  in  the  gas  increases.     Within 
a  half  hour  the  larger  part  of  the  volatile  matters  may  have  dis- 
tilled off  leaving  the  gas  almost  free  from  hydrocarbons  and  from 
tar  vapors.     Rapid  changes  will  also  be  noted  after  poking  the 
fire. 

An  average  sample  of  producer  gas  may  be  obtained  only 
by  extending  the  sampling  over  a  long  period,  as  directed  in 
Chapter  I.  There  will  be  especial  difficulty  in  determining  the 
quantity  and  heat  value  of  the  suspended  tarry  particles.  Yet 
these  values  must  be  ascertained  if  the  heat  value  of  the  crude 
gas  is  to  be  determined  accurately.  The  method  of  collecting 
the  tar  particles  on  filter  papers,  given  in  Chapter  IX,  may  be 
followed  and  the  weight  of  tar  per  cubic  foot  of  gas  thus  obtained. 
The  papers  and  tar  may  then  be  burned  in  a  bomb  calorimeter 
and  after  deduction  of  the  heat  due  to  the  known  amount  of 
filter  paper,  the  heating  value  of  the  tar  may  be  obtained.  This 
determination  is  not  often  made,  as  it  is  difficult  to  carry  it  out 
accurately.  However,  it  is  not  possible  to  find  the  true  heat 
balance  on  a  furnace  fired  with  crude  producer  gas,  especially  if 
from  a  bituminous  producer,  unless  such  a  determination  is  made. 

Ordinarily  the  determination  of  tar  and  suspended  particles 
is  neglected  and  the  sampling  then  is  to  be  conducted  as  described 
in  Chapter  I. 

3.  Analysis    of    Producer    Gas. — The    constituents    to    be 
determined  in  producer  gas  are   carbon  dioxide,   unsaturated 
hydrocarbons,  oxygen,  carbon  monoxide,  hydrogen  and  methane. 
The  methods  are  given  in  Chapters  II,  III  and  IV.     No  difficulty 
will  be  experienced  except  with  hydrogen  and  methane.     The 
percentage  of  these  gases,  except  in  water  gas,  is  usually  so  small 
that  a  sample  after  removal  of  the  absorbable  constituents  is  no 
longer  explosive  when  mixed  with  air.     It  should  be  emphasized 
that  failure  to  obtain  an  explosion  does  not  mean  the  absence 
of  hydrogen  and  methane  but  merely  that  they  are  present  in 
less  than  explosive  amounts.     Explosion  may  be  brought  about 
by  addition  of  a  known  volume  of  pure  hydrogen  to  form  an 
explosive  mixture  but  it  is  usually  simpler  to  use  a  method  which 


PRODUCER  GAS  159 

does  not  involve  explosion.  Combustion  with  a  hot  platinum 
spiral  as  in  the  Dennis  and  Hopkins  method  (§  9  of  Chapter  IV) 
or  with  copper  oxide  as  in  the  Jaeger  method  (§  11  of  Chapter 
IV)  affords  a  satisfactory  method  for  determination  of  these 
constituents. 

4.  Interpretation  of  Analysis.— The  important  constituents 
are  carbon  dioxide  and  carbon  monoxide.  Oxygen  should  be 
entirely  absent,  as  it  should  all  have  been  brought  into  combina- 
tion in  its  passage  through  the  producer.  Its  presence  in  a  pro- 
ducer gas  may  be  an  indication  of  leakage  in  sampling  or  of 
leakage  into  the  flue  prior  to  sampling.  Rarely,  if  operating 
conditions  in  the  producer  are  bad,  and  the  fire  is  thin,  there 
may  be  such  a  channel  formed  in  the  producer  that  air  will 
rush  through  the  producer  without  its  oxygen  becoming  combined. 
Such  a  condition  will  be  indicated  by  extremely  high  carbon 
dioxide,  with  low  percentages  of  combustible  gases.  When  a 
producer  is  running  under  normal  conditions  its  operation  may 
be  quite  closely  checked  by  the  percentage  of  carbon  dioxide 
alone.  High  carbon  dioxide  is  in  practically  all  cases  an  un- 
favorable symptom.  It  may  be  due  to  a  cold  fuel  bed  in  the 
producer  caused  either  by  an  excess  of  steam  or  by  slow  running, 
it  may  be  due  to  a  thin  fuel  bed  which  does  not  allow  sufficient 
time  and  contact  for  the  reduction  of  the  carbon  dioxide  to 
monoxide,  and  it  may  be  due  to  channels  or  chimneys  in  a  deep 
fire  which  allow  uncombined  air  to  get  through  the  fuel  bed  and 
burn  above  the  coals. 

A  cold  fuel  bed  in  a  producer  burning  bituminous  coal  will 
tend  to  increase  the  percentage  of  unsaturated  hydrocarbons, 
but  in  no  case  will  they  amount  to  more  than  a  few  tenths  of  a 
per  cent.  A  hot  and  thin  fuel  bed  and  especially  a  channeled 
fuel  bed  will  cause  the  unsaturated  hydrocarbons  to  practically 
disappear,  since  they  are  decomposed  at  the  high  temperature 
and  of  all  the  gases  show  the  greatest  avidity  for  oxygen. 

The  carbon  dioxide  is  almost  a  direct  measure  of  the  thermal 
efficiency  of  the  producer,  the  only  exception  being  its  appear- 
ance as  the  result  of  the  interaction  of  carbon  and  steam  at  a 
relatively  low  temperature  as  in  the  Mond  producer  where  it 
is  accompanied  by  a  high  percentage  of  hydrogen.  Under  other 
circumstances  high  carbon  dioxide  means  low  thermal  efficiency 


160  GAS  AND  FUEL  ANALYSIS 

for  the  70  per  cent,  of  the  energy  of  the  carbon  which  should 
have  been  converted  into  the  potential  energy  of  the  carbon 
monoxide  is  all  changed  to  the  sensible  heat  of  the  carbon 
dioxide  and  accompanying  gases. 

6,  Heating  Value  of  Producer  Gas. — The  heating  value  of 
producer  gas  may  be  determined  in  a  calorimeter  as  described 
in  Chapter  VII  for  illuminating  gas.  A  special  tip  must  be 
used  on  the  burner  and  care  be  taken  to  see  that  the  flame 
burns  clear.  The  heating  value  of  producer  gas  may  be  as 
low  as  100  British  thermal  units  per  cubic  foot  and  it  frequently 
happens  that  it  does  not  burn  readily  in  a  Bunsen  burner. 
The  gas  must  be  carefully  cooled  and  cleaned  before  testing. 
This  operation  separates  tar  whose  amount  and  heat  value  must 
be  determined  as  directed  in  §  2  of  this  chapter.  The  heating 
value  of  the  purified  gas  may  also  be  calculated  from  the 
analysis  as  indicated  in  §  17  of  Chapter  VII.  The  low  per- 
centage of  unsaturated  hydrocarbons  in  producer  gas  makes 
the  errors  of  calculation  less  than  is  the  case  with  illuminating 
gas.  On  account  of  the  difficulty  in  cleaning  the  gas  and  in 
keeping  a  steady  flame  in  the  calorimeter,  the  heating  value  is 
usually  obtained  by  calculation. 

It  is  worth  while  to  emphasize  again  that  the  heating  value 
of  the  cleaned  gas  from  bituminous  coal  is  lower  than  that  of 
the  hot  gas  which  still  contains  tar  vapors  and  that  allowance 
must  be  made  for  the  tar  vapors  in  calculating  the  heat  value  of 
the  gas  which  is  used  while  hot. 

6.  Volume  of  Producer  Gas. — It  would  be  very  desirable  to 
be  able  to  calculate  the  volume  of  producer  gas  per  pound  of 
coal,  as  is  done  in  Chapter  X  for  chimney  gases.  There  are,  how- 
ever, so  many  possible  reactions  in  the  gas  producer  and  the 
changes  in  volume  are  so  complicated,  especially  in  a  bituminous 
producer,  that  it  is  only  possible  to  make  such  calculations  for 
simple  cases. 

Assume  a  producer  burning  pure  carbon  in  dry  air.  It  is 
manifest  that  the  only  products  of  combustion  will  be  C02,CO 
and  N2  Assume  the  following  composition  of  the  gas 

COj 5.5  per  cent. 

CO 25 . 6  per  cent. 

N2 68.9  per  cent, 


PRODUCER  GAS  161 

The  air  entering  the  producer  was  composed  of  79  volumes 
of  nitrogen  for  every  21  volumes  of  oxygen.  The  change  in 
percentage  of  the  nitrogen  in  the  producer  gas  is  due  to  changes 
resulting  from  the  union  of  oxygen  with  carbon.  The  first  step 
is  to  trace  the  changes  taking  place  when  100  volumes  of  air  pass 
through  the  producer  and  find  the  relative  volumes  of  C02  and 
CO  for  79  volumes  of  N2. 

7Q 
CO2    5.5X-=  6.3=  6.3vols.  O2 


79 
CO   25.6Xgg^=29.4  =  14.7  vols.  O2 

79 

.  N2 


100.0  vols.  air. 

One  pound  of  carbon  burning  to  carbon  dioxide  requires  32.1 
cu.  ft.  of  oxygen  (at  60°  F.  and  30  in.  of  mercury  pressure)  and 
yields  32.  1  cu.  ft.  of  carbon  dioxide.  One  pound  of  carbon  burning 
to  carbon  monoxide  requires  16.05  cu.  ft.  of  oxygen  and  yields 
32.1  cu.  ft.  of  carbon  monoxide.  It  follows  that  the  weights  of 
carbon  burning  to  CO  and  CO2  are  proportional  to  the  volumes 
of  the  two  gases.  In  the  present  instance 

CO2    6.  3=^7X100  =  17.  7  per  cent. 

oq  4 
CO   29.  4=~*X100  =  82.3  per  cent. 


One  pound  of  carbon  yields 

0.177X32.1=     5.7cu.  ft.  CO2 
0.823X32.1=  26.4cu.  ft.  CO 
3.76   X32. 1  =  120.7  cu.  ft.     N2 

152 . 8  cu.  ft.  producer  gas. 

The  sensible  heat  will  be  calculated  as  in  Chapter  X. 

5. 7 X. 0268X1000=   153  B.  t.  u. 
26.4 
120^7 
147.1X.0180X1000  =  2647  B.  t.  u. 

2800  B.  t.  u. 
11 


162  GAS  AND  FUEL  ANALYSIS 

l  Energy  in  26.4  cu.  ft.  of  CO  8540  B.  t.  u. 

Sensible  heat  in  gases  2800  B.  t.  u. 

Total  energy  in  gas  at  1000°  F.      11340  B.  t.  u. 
Efficiency  of  producer  when  gas  is  ueed  at 

1000°  F.  =  X  100  =  77.6  per  cent' 


7.  Efficiency  of  a  Gas  Producer.  —  In  the  simple  instance  cited 
above  it  is  easy  to  calculate  the  energy  contained  in  the  gas. 
The  only  potential  energy  in  the  gas  from  one  pound  of  carbon 
is  contained  in  the  0.823  lb.,  which  is  now  in  the  form  of  26.4  cu. 
ft.  carbon  monoxide.  The  heating  value  of  this  is: 

26.4X323.5=  8540  B.t.u. 

The  total  energy  of  the  coal  if  burned  to  carbon  dioxide  would 
be  14600  British  thermal  units.  If  the  gas  is  cooled  before  being 
burned  so  that  its  only  energy  is  the  potential  energy  of  the  carbon 
monoxide  the  efficiency  of  the  producer  is 


8540^ 
14600 


^X 100  =  58 .5  percent. 


If  the  gas  is  burned  while  still  hot,  say  at  1000°  F.,  there  should 
be  credited  to  the  producer  also  the  sensible  heat  of  the  gas,  as 
calculated  in  the  preceding  section  where  the  efficiency  was  shown 
to  be  77.6  per  cent. 

The  above  simple  relations  do  not  hold  when  steam  is  being 
injected  into  the  producer  with  the  air  nor  when  bituminous  coal 
is  being  used  as  a  fuel.  On  account  of  the  varied  possibilities  of 
chemical  reaction  in  these  cases  the  volume  of  the  gases  cannot 
be  calculated  from  their  chemical  composition.  If  the  volume 
of  the  gases  is  measured  by  a  Venturi  meter,  or  otherwise,  then  it 
is  possible  to  calculate  the  sensible  and  potential  energy  of  the 
gases  as  indicated  in  this  chapter  and  the  one  preceding. 


_ 

CHAPTER  XII 

ILLUMINATING  GAS  AND  NATURAL  GAS 

1.  Introduction. — Chemical   analysis  plays  a  minor  role  in  \ 
testing  illuminating  gas  and  natural  gas.     The  determination  ',. 
of  heating  value  is  described  in  Chapter  VII  and  of  candle-power 
in  Chapter  VIII.     The  ordinary  chemical  analysis  as  described 
in  Chapters  III  and  IV  usually  includes  the  determination  of 
carbon  dioxide,  unsaturated  hydrocarbons,  oxygen,  carbon  mon- 
oxide, hydrogen  and  methane,  nitrogen  being  taken  by  difference. 
A  separate  determination  of  benzene  is  sometimes  desired  in 
illuminating  gas  and  of  gasoline  vapors  in  natural  gas.     Sulphur 
may  be  called  for  in  both  gases.     Naphthalene  and  ammonia  are  / 
frequently  determined  in  coal  gas. 

2.  Sampling. — The  sampling  of  natural  gas  and  of  purified 
illuminating  gas  usually  offers  little  difficulty,  since  the  gases 
are  thoroughly  mixed  and  contain  such  small  amounts  of  sus- 
pended  particles  that  they  are  usually  negligible.     The  chief 
point  to  be  observed  in  sampling  from  service  pipes  in  cities  is  to 
see  that  the  gas  is  allowed  to  run  long  enough  to  flush  out  the 
pipe  and  bring  to  the  sampling  cock  gas  which  is  representative 
of  that  flowing  in  the  mains.     Illuminating  gas  of  high  candle- 
power  must  not  become  chilled  in  the  sampling  process,  for  there 
is  danger  of  condensing  the  benzene  or  other  hydrocarbon  vapors 
which  it   contains.     Rubber   connections  are  also  to  be  mini- 
mized in  sampling  because  of  the  solubility  of  the  hydrocarbons 
in  rubber.     The  water  used  in  the  sampling  vessels  must   be 
carefully  saturated  before  use,  because  unsaturated  hydrocarbons 
are  relatively  soluble  in  water. 

In  case  unpurified  illuminating  gas  is  to  be  sampled,  additional 
precautions  must  be  taken  on  account  of  the  presence  of  material 
amounts  of  ammonia,  hydrogen  sulphide,  carbon  dioxide  and 
other  very  soluble  gases,  as  well  as  suspended  tar  particles.  In 
case  it  is  sufficient  to  determine  what  the  approximate  composi- 
tion of  the  gas  would  be  after  purification  it  is  sufficiently  accu- 

163 


164  GAS  AND  FUEL  ANALYSIS 

rate  to  sample  in  the  usual  way  and  trust  the  water  of  the  samp- 
ling tank  to  remove  the  ammonia,  hydrogen  sulphide  and  part 
of  the  carbon  dioxide.  In  case  the  actual  composition  of  the 
unpurified  gas  is  desired,  these  soluble  constituents  must  be 
separately  determined  as  indicated  in  succeeding  sections. 

3.  General  Scheme  of  Analysis. — Carbon  dioxide,  unsaturated 
hydrocarbons,  oxygen,  carbon  monoxide,  hydrogen  and  methane 
are  usually  determined  according  to  the  methods  of  Chapters  III 
and  IV.     In  the  case  of  unpurified  illuminating  gas  there  may 
be  appreciable  amounts  of  hydrogen  sulphide  absorbed  with  the 
carbon  dioxide.     If  it  is  desired  to  separate  the  two  the  hydrogen 
sulphide  may  be  estimated  according  to  the  method  of  §  7  of 
this  chapter.     The  estimation  of  carbon  dioxide,  oxygen  and 
carbon  monoxide  does  not  present  any  peculiarities,  although 
emphasis  should  be  laid  on  the  necessity  of  complete  removal  of 
the  unsaturated  hydrocarbons  before  the  estimation  of  oxygen 
by  phosphorus.     In  the  case  of  Pintsch  gas  it  sometimes  requires 
five  minutes  shaking  with  bromine  water  to  affect  such  a  com- 
plete removal  of  the  hydrocarbons  that  the  phosphorus  will 
smoke  when  the  gas  is  subsequently  passed  over  it.     The  deter- 
mination of  hydrogen  and  methane  in  illuminating  gas  offers  no 
marked  peculiarity.     In  natural  gas,  higher  hydrocarbons  are 
present  and  complicate  the  calculation.     Ethane  may  be  present 
in  natural  gas  and  also  in  water  gas  and  Pintsch  gas.     The 
methods  for  its  determination  have  been  discussed  in  Chapter 
IV.     Nitrogen  is  taken  by  difference  and  as  the  analysis  is  a 
rather  long  and  complicated  one,  the  errors  piling  up  on  the 
nitrogen  are  apt  to  be  material.     A  direct  combustion  of  the  gas 
with  copper  oxide,  as  described  in  §  12  of  Chapter  IV,  gives  a 
more  accurate  determination  of  the  residual  nitrogen. 

4.  Chemical  Composition  of  Illuminating  Gas. — The  so-called 
" coal  gas"  is  made  by  the  destructive  distillation  of  coal  in  closed 
retorts.  '  The  composition  of  the  gas  is  dependent  on  the  compo- 
sition of  the  coal,  the  temperature  of  the  retort  and  to  some  extent 
its  shape  and  size.     There  is  nothing,  however,  which  distinctly 
characterizes  gas  from  the  large  retort  of  the  by-product  coke 
oven  from  that  of  the  small  horizontal  retort  of  the  gas  works. 
The  oxygen  of  the  coal  appears  in  the  gas  partly  as   carbon 
dioxide,  partly  as  carbon  monoxide,  and  partly  as  water  vapor. 


ILLUMINATING  GAS  AND  NATURAL  GAS 


165 


None  of  it  will  be  evolved  as  gaseous  oxygen.  The  carbon  mon-J 
oxide  will  be  greater  at  a  high  temperature  than  at  a  low  one,  but 
will  usually  stay  between  the  limits  of  5  and  9  per  cent.  A  high 
retort  temperature  will  cause  cracking  of  the  hydrocarbons  with 
decrease  of  their  percentage  and  increase  of  hydrogen.  A  frac- 
tion of  1  per  cent,  of  free  oxygen  is  normally  present  in  illumin- 
ating gas,  partly  because  of  air  entering  during  the  operation  of 
charging  and  drawing  the  retort,  partly  because  of  leaks  in  the 
long  condensing  system  and  partly  because  of  liberation  of  the 
oxygen  dissolved  in  the  water  used  in  the  scrubbers.  In  so  far 
as  this  oxygen  comes  from  the  air  it  must  be  accompanied  by  four 
volumes  of  nitrogen.  Nitrogen  must  always  be  present  in  this 
amount.  Less  than  four  volumes  of  nitrogen  for  one  of  oxygen 

TYPICAL  ANALYSES  OF  ILLUMINATING  GAS 


1 

2 

3 

4 

5 

C6H6 

* 

1.2 

0  2 

* 

1.3 

CO2 

1  5 

1  4 

1  3 

2  7 

3  5 

CnH2n  

4.6 

4.0 

2.0 

6.5 

11.6 

O2  

0  3 

0.9 

0.5 

1.1 

0.7 

CO  

7.1 

4.6 

4.8 

12.4 

31.6 

H2  

46.4 

49.6 

50.7 

38.4 

35.7 

CH4  

36.3 

35.0 

38.1 

28.4 

9.0 

N2      . 

3.7 

3.3 

2.4 

10.5 

3.7 

C2H6  2.9 

*  Not  separately  reported. 

1.  Coal  gas  of  17  c.p.  and  650  B.t.u. 

2.  Coke  oven  gas  enriched  by  benzol  to  16.4  c.p.  and  626  B.t.u.  (Proc. 
Am.  Gas  Inst.,  6,  519  (1911).) 

3.  Coke  Oven  Gas.     Fuel  Gas  (Proc.  Am.  Ga*  Inst.,  6,  519  (1911).) 

4.  Mixed  Coal  and  Water  Gas  15  c.p.  and  615  B.t.u. 

5.  Carbureted  Water  Gas  of  24  c.p.  and  649  B.t.u.  (Proc.  Am.  Gas  Inst., 
7,  739  (1912).) 

indicates  a  faulty  analysis.  The  unavoidable  nitrogen  in  the  gas 
arising  from  the  destructive  distillation  of  the  nitrogenous  com- 
pounds of  the  coal  will  be  between  1  and  1.5  per  cent.  High 
percentages  of  nitrogen  unaccompanied  by  a  corresponding 
amount  of  oxygen  indicate  that  suction  has  been  maintained 
on  the  porous  retorts,  so  that  air  has  been  sucked  in.  The 
oxygen  thus  brought  in  contact  with  the  hot  gas  will  at  once  burn 
with  formation  of  carbon  dioxide  or  water  while  the  nitrogen  will 


166  GAS  AND  FUEL  ANALYSIS 

remain  and  appear  as  such  in  the  purified  gas.  In  the  manufac- 
ture of  water  gas  a  high  percentage  of  nitrogen  will  result  if  the 
gasmaker  turns  the  gas  into  the  holder  before  all  the  gas  pro- 
duced while  blowing  air  is  flushed  from  the  machine  by  the  water 
gas. 

5.  Benzene. — Benzene  is  a  normal  constituent  of  coal  gas  and 
also  probably  of  water  gas,  but  its  amount  in  unenriched  coal 
gas  is  always  less  than  1  per  cent.,  and  it  is  not  usually  deter- 
mined. Its  solubility  in  water  and  in  caustic  soda  is  slight  so 
that  in  the  ordinary  analysis  the  benzene  is  not  absorbed  by  the 
caustic  but  passes  on  to  the  bromine  pipette  where  it  dissolves  in 
the  ethylene  bromide  formed  in  the  reaction  between  ethylene 
and  bromine  and  is  therefore  estimated  with  the  ethylene  as 
"illuminants."  As  benzene  has  a  very  high  illuminating  power 
this  grouping  is  logical  and  sufficiently  satisfactory  for  most 
purposes. 

Hempel  recommends  that  1  c.c.  of  absolute  alcohol  be  placed 
in  a  pipette  otherwise  filled  with  mercury.  An  explosion  pipette 
answers  well  for  this  purpose.  A  sample  of  gas  is  to  be  passed 
into  the  pipette  and  shaken  with  the  alcohol  to  saturate  it  with 
ethylene,  and  the  sample  to  be  analyzed  is  later  passed  into  this 
same  pipette  and  shaken  three  minutes.  The  gas  is  then  drawn 
back  into  the  burette  and  passed  into  a  second  mercury  pipette 
containing  1  c.c.  of  distilled  water  which  removes  the  alcohol 
vapors.  The  decrease  in  volume  from  the  initial  reading  is 
recorded  as  benzene.  The  method  is  to  be  considered  only  an 
approximate  one. 

Morton1  recommends  that,  after  removal  of  carbon  dioxide 
by  caustic  soda  as  usual,  the  gas  be  passed  into  an  ordinary 
simple  absorption  pipette  containing  concentrated  sulphuric 
acid  (sp.  gr.  1.84)  and  shaken  vigorously  for  one  minute.  The 
decrease  in  volume  after  drawing  back  into  the  burette  represents 
benzene.  Dennis  and  McCarthy2  dispute  the  accuracy  of  this 
method  and  propose  ammoniacal  nickel  cyanide  as  a  reagent. 
The  gas  after  carbon  dioxide  has  been  removed  by  caustic  is 
passed  into  the  pipette  containing  the  ammoniacal  nickel  cyanide 
solution  and  drawn  back  and  forth  between  the  burette  and 

1  Jour.  Am.  Chem.  Soc.,  28,  1728  (1906). 

2  Jour.  Am.  Chem.  Soc.,  30,  233  (1908). 


ILLUMINATING  GAS  AND  NATURAL  GAS  167 

pipette  for  about  two  minutes.  It  is  then  passed  into  a  five  per 
cent,  solution  of  sulphuric  acid  and  shaken  until  the  ammonia 
is  absorbed,  which  requires  about  two  minutes.  According  to  the 
authors,  the  absorption  is  quantitative  and  the  result  unaffected 
by  ethylene. 

The  process  of  Haber  and  (Echelhauser1  is  based  on  Bunte's 
observation  of  the  solubility  of  benzene  in  ethylene  bromide. 
The  authors  treat  the  gas  with  a  fresh  solution  of  bromine  water 
to  which  is  added,  immediately  after  the  reaction  an  excess  of 
strong  potassium  iodide.  The  liberated  iodine  is  titrated 
with  thiosulphate  and  the  difference  between  the  figures  of 
this  titration  and  those  obtained  by  a  blank  test  on  an  equal 
volume  of  the  original  solution  represents  the  bromine  which 
has  combined  with  the  ethylene.  One  cubic  centimeter  deci- 
normal  thiosulphate  corresponds  to  1.12  c.c.  ethylene  at  0°  C. 
and  760  mm.  or  to  1.22  c.c.  at  60°  F.  and  29.5  in.  mercury  pres- 
sure. The  diminution  in  volume  of  the  gas  after  the  usual  treat- 
ment with  bromine  water  followed  by  caustic  gives  the  sum  of 
the  benzene  and  ethylene.  The  difference  between  this  volume 
and  that  indicated  by  the  titration  for  ethylene  gives  the  benzene. 

If  a  more  exact  method  of  estimation  of  benzene  is  desired 
and  a  large  sample  of  gas  can  be  obtained  the  method  of  Harbeck 
and  Lunge2  may  be  used.  It  consists  in  aspirating  10  liters 
of  the  gas  through  a  mixture  of  equal  weights  of  fuming  nitric 
acid  and  concentrated  sulphuric  acid.  Part  of  the  resulting 
dinitrobenzene  crystallizes  out  after  the  acids  are  diluted, 
cooled  and  neutralized,  and  may  be  filtered  and  weighed.  The 
dinitrobenzene  remaining  in  solution  is  extracted  from  an  ali- 
quot portion  of  the  filtrate  with  ether  and  also  weighed. 

6.  Benzene  and  Light  Oils  by  Differential  Pressure  Method. 
Davis  and  Davis3  have  described  a  differential  pressure  method 
for  determining  benzene  and  light  oils  which  requires  relatively 
small  samples  of  gas.  The  apparatus  as  illustrated  in  Fig.  37 
consists  of  a  pair  of  flasks  connected  by  a  differential  manometer. 
The  saturation  vapor  pressure  of  a  liquid  is  a  function  of  the 
temperature  and  is  independent  of  the  amount  of  liquid  (provided 

1  Jour,  fiir  Gasbel,  43,  347  (1900). 

*Zeit.  fiir  anorg.  Chem.,  16,  41  (1898). 

3  J.  Ind.  &  Eng.  Chem.,  10,  709-718  (1918). 


168 


GAS  AND  FUEL  ANALYSIS 


there  is  an  excess  of  liquid  after  saturation  is  reached)  and  of  the 
pressure  on  the  inert  gas  into  which  it  evaporates.  If  each  of  the 
flasks  A'  and  B  in  Fig.  37  is  filled  with  air  and  closed,  the  mano- 
meter will  show  no  pressure  difference  between  them.  If  now 

the  small  bulb  a  containing 
benzene  is  broken,  the  benzene 
will  evaporate  into  A  and  the 
manometer  will  after  equilib- 
rium is  reached,  show  an  in- 
creased pressure  in  the  vessel 
corresponding  to  the  satura- 
tion pressure  for  benzene; 
since  the  flask  B  contains  air 
with  no  benzene.  If  flask  B 
is  filled  with  coal  gas  at 
atmospheric  pressure  and  the 
flasks  are  closed  the  manom- 
eter will  indicate  no  pressure 
difference.  If  the  bulbs  a  and 
6  containing  benzene  are  now 
broken  the  vapor  pressure  in 
A  will  rise  as  before  but  the 
vapor  pressure  in  B  will  not 
increase  so  much  since  the 
gas  in  B  had  already  con- 
tained some  benzene  vapors. 
The  manometer  connecting 
the  two  flasks  will  therefore 
register  a  pressure  equal  to 
the  partial  pressure  of  the 
benzene  originally  in  B,  from 


FIG.  37. — Davis  differential  pressure 
apparatus  for  benzene  in  gas. 


which  the  amount  of  benzene  in  the  original  gas  can  be  calcu- 
lated. Coal  gas  carries  not  only  benzene  but  also  toluene  and 
small  amounts  of  other  hydrocarbon  vapors.  The  liquid  in  the 
bulbs  should  therefore  be  light  oil  instead  of  benzene  and  under 
such  circumstances  the  reading  will  give  percentage  of  light  oil 
vapors.  If  benzene  alone  is  to  be  determined  the  flasks  must 
be  cooled  to  almost  the  freezing  temperature  of  benzene,  at 
which  temperature  the  vapor  pressure  of  the  other  constituents 
is  negligible. 


ILLUMINATING  GAS  AND  NATURAL  GAS  169 

7.  Hydrogen  Sulphide. — Hydrogen  sulphide  should  be  present 
only  in  minute  traces  in  purified  illuminating  gas.  The  usual 
test  is  an  approximate  one  based  on  the  reaction  of  hydrogen 
sulphide  and  lead  acetate  to  form  black  lead  sulphide.  A  strip 
of  white  filter  paper  moistened  with  colorless  lead  acetate  is 
exposed  to  the  gas  and  the  depth  of  the  resulting  black  stain 
noted.  The  details  of  the  test  differ  widely.  The  New  York 
State  Commission  prescribes  that  gas  shall  show  no  hydrogen 
sulphide  when  tested  by  exposing  the  paper  moistened  with  lead 
acetate  to  a  current  of  gas  burning  at  the  rate  of  5  cu.  ft.  per 
hour.  The  paper  must  not  become  discolored  after  thirty  sec- 
onds of  such  exposure.  Ramsburg1  and  McBride,2  Weaver  and 
Edwards  have  given  a  full  discussion  of  the  various  methods  of 
testing  for  hydrogen  sulphide  in  gas. 

Hydrogen  sulphide  is  always  present  in  unpurified  illuminating 
gas.  In  the  ordinary  gas  analysis  it  is  absorbed  by  the  caustic 
soda  simultaneously  with  the  carbon  dioxide  and  reported  with 
it.  Its  quantitative  estimation  may  be  carried  out  as  follows. 
One  or  more  liters  of  the  gas  is  bubbled  through  a  solution  of 
ammoniacal  cadmium  chloride  and  the  resultant  cadmium  sul- 
phide is  filtered.  If  the  precipitate  contains  much  tar  it  may  be 
washed  on  the  filter  with  benzol.  Place  filter  and  precipitate 
in  cold  dilute  hydrochloric  acid  till  dissolved  and  titrate  with 
standard  iodine.  If  the  iodine  solution  is  made  by  dissolving 
1.0526  grm.  iodine  to  the  liter,  1  c.c.  will  be  equivalent  to  1/10 
c.c.  of  hydrogen  sulphide  measured  damp  at  60°  F.  and  under 
30  in.  of  mercury  pressure.  A  solution  of  ten  times  the  above 
strength  is  more  convenient  if  much  hydrogen  sulphide  is  present. 

A  rapid  approximate  estimation  of  hydrogen  sulphide  may  be 
made  in  the  Bunte  gas  burette  described  in  §  4  of  Chapter  V. 
The  burette  is  first  filled  with  water  containing  a  little  thin 
starch  paste  to  act  as  indicator,  and  the  sample  of  gas  drawn  in 
and  measured  rapidly  to  prevent  error  due  to  the  solubility  of 
the  hydrogen  sulphide  in  the  water  of  the  burette.  Standard 
iodine  solution  is  now  admitted  from  the  reservoir  at  the  top  of 
the  burette,  about  a  cubic  centimeter  at  a  time,  until  the  blue 
color  formed  by  the  reaction  between  the  iodine  and  starch 

1  Proceedings  Am.  Gas.  Inst.,  4,  453,  1909. 

2  Technologic  Papers  20  and  41,  Bureau  of  Standards. 


170 


GAS  AND  FUEL  ANALYSIS 


persists  after  repeated  shaking,  showing  that  the  hydrogen  sul- 
phide has  all  been  oxidized.  If  iodine  solution  of  the  concentra- 
tion given  above  has  been  used,  the  volume  of  hydrogen  sulphide 
may  be  read  directly  from  the  volume  of  iodine  used,  which  must 
be  obtained  by  measuring  the  iodine  solution  still  remaining  in 
the  reservoir  of  the  burette.  Tutwiler  has  modified  the  burette 

by  making  the  reservoir  longer  and 
graduating  it  so  that  the  iodine  used 
may  be  read  directly. 

8.  Total  Sulphur  Compounds. — Illu- 
minating gas  and  almost  all  other  gases 
used  for  fuel  contain,  in  addition  to 
hydrogen  sulphide,  compounds  of  sulphur 
and  carbon  such  as  carbon  bisulphide 
and  more  complex  compounds  like  the 
mercaptans.  These  compounds  are 
usually  estimated  after  complete  com- 
bustion, in  which  process  all  the  sulphur, 
whatever  its  previous  combination,  is 
converted  into  sulphur  dioxide  and 
sulphur  trioxide.  These  gases  are  ab- 
sorbed, oxidized  to  sulphuric  acid  and 
weighed  as  barium  sulphate.  Care 
must  be  taken  to  see  that  the  air  used 
for  combustion,  which  is  usually  ten 
times  the  volume  of  the  gas,  is  itself 
free  from  sulphur  compounds,  and  that 
combustion  is  complete.  The  form  of 
burner  and  absorption  apparatus  is 
immaterial,  except  for  convenience. 

The  older  design  due  to  Drehschmidt  has  been  modified  by 
Harding,1  Jenkins,2  and  the  Bureau  of  Standards.3  -Any  of  these 
modifications  may  be  made  from  ordinary  laboratory  apparatus. 
The  apparatus  described  and  illustrated  in  Fig.  38  is  that  of  the 
Bureau  of  Standards.  The  entire  apparatus  consists  of  pressure 
regulator,  U  water  gage,  meter,  sulphur  apparatus,  wash  bottles, 

1  Jour.  Am.  Chem.  Soc.,  28,  537  (1906). 

2  Jour.  Am.  Chem.  Soc.,  28,  542  (1906). 

3  Circular  No.  48,  Bureau  of  Standards. 


FIG.  38.  —Bureau  of 
standards  form  of  sulphur 
apparatus. 


ILLUMINATING  GAS  AND  NATURAL  GAS  171 

and  jet  pump,  connected  in  the  order  named;  soda-lime  tower  for 
the  purification  of  the  air;  and  battery  and  spark  coil,  connected 
( to  the  burner.  The  burner  is  a  porcelain  tube  of  3-4  mm.  internal 
diameter.  The  gas  is  ignited  by  an  electric  spark  between  plati- 
num terminals  which  are  soldered  to  nickel  leads,  in  order  that 
only  a  short  length  of  platinum  wire  will  be  needed.  One  of  the 
leads  is  placed  within  the  burner  tube,  its  lower  end  being  brought 
j  out  through  a  small  side  tube  which  is  sealed  to  the  glass  tube 
just  below  the  rubber  stopper;  the  wire  can  be  held  in  place  and 
the  opening  closed  by  sealing  wax.  The  terminal  outside  is 
wired  to  the  porcelain  burner  tube.  The  platinum  wire  becomes 
heated  by  the  flame  and  thus  reduces  the  likelihood  that  the 
flame  will  be  extinguished  by  fluctuations  in  gas  pressure.  This 
igniter  therefore  eliminates  the  principal  difficulty  both  of  lighting 
and  of  regulating  the  burner  which  is  experienced  with  apparatus 
of  this  type. 

The  stopper  which  closes  the  lower  end  of  the  combustion 
chamber  also  serves  as  a  connector,  the  porcelain  burner  tube  and 
the  glass  T  piece  being  firmly  fastened  into  it  by  means  of  Kho- 
tinsky  or  sealing  wax.  The  small  tip  through  which  the  gas 
enters  just  above  the  primary  air  inlet  is  also  held  in  with  Kho- 
tinsky  cement.  The  tip  can  be  easily  removed  for  cleaning,  or 
tips  of  various  sizes  adapted  to  the  gas  to  be  burned  can  be 
inserted.  The  air  necessary  for  complete  combustion  after  being 
purified  by  passage  through  the  large  soda-lime  tower  is  supplied 
to  the  flame  in  two  portions.  The  primary  air  is  drawn  in  by  the 
gas  as  it  passes  through  the  small  tip;  the  secondary  air  enters 
through  the  two  inlets  at  the  side  of  the  combustion  chamber. 

The  combustion  chamber,  made  of  Pyrex  glass  tubing,  is  about 
360  mm.  long  and  about  25  mm.  in  internal  diameter.  The  nar- 
row tube  at  the  top  may  be  used  for  introducing  water  when  it 
is  desired  to  rinse  out  the  apparatus;  when  in  operation  this 
tube  is  closed  with  a  small  cork.  Satisfactory  drainage  is  pro- 
vided by  the  sloping  layer  of  paraffin  or  sealing  wax  covering  the 
stopper  at  the  bottom.  When  the  burner  is  lighted  the  second- 
ary inlet  air  keeps  the  base  of  the  apparatus  cool,  but  the  rest  of 
the  combustion  chamber  up  to  the  side  tube  is  heated  so  that  no 
condensation  takes  place  on  the  walls.  For  that  reason  it  is 
usually  unnecessary  to  rinse  out  the  combustion  chamber.  By 


172  GAS  AND  FUEL  ANALYSIS 

means  of  a  cork  connector  the  first  of  a  series  of  wash  bottles  is 
attached  to  the  apparatus.  Rubber  tubing  must  not  be  used 
at  this  point  on  account  of  the  danger  of  introducing  sulphur  from 
it;  but  the  wash  bottles  may  be  connected  to  each  other  and  to 
the  suction  pump  by  rubber  tubing,  which  may  also  be  used 
to  connect  the  air  inlets  to  the  soda  lime-tower  Only  one  wash 
bottle  is  shown  in  the  illustration,  but  three  are  usually  required 
for  satisfactory  operation.  In  order  that  the  suction  may  pull 
the  gas  steadily  through  the  wash  bottles  it  is  necessary  that  the 
end  of  the  inlet  tube  of  the  first  bottle  be  perforated  with  a 
number  of  small  holes.  With  a  single,  large  opening  the  opera- 
tion of  the  burner  is  not  steady.  The  wash  bottles  may  be  of 
any  of  the  ordinary  forms.  Each  bottle  should  contain  enough 
absorbent  so  that  the  products  of  combustion  will  bubble  through 
a  depth  of  1  to  lj^  inches  of  liquid.  The  air  is  drawn  in  and  the 
products  of  combustion  are  drawn  through  the  apparatus  by  the 
suction  of  a  small  water  jet  pump,  or  its  equivalent.  The  spark 
for  igniting  gas  is  produced  by  a  single  dry  cell  and  an  induc- 
tion coil  of  the  size  rated  as  giving  a  quarter-inch  spark. 

Before  beginning  a  determination  the  apparatus  should  be 
adjusted  to  burn  gas  at  the  required  rate,  not  more  than  2.5 
cu.  ft.  per  hour,  and  to  use  the  proper  amount  of  primary  and 
secondary  air.  The  amount  of  gas  burned  should  be  adjusted 
by  removing  the  small  glass  inlet  tip  from  the  burner  and  reduc- 
ing or  enlarging  the  opening  as  required.  The  opening  may  be 
reduced  by  heating  carefully  in  a  flame;  it  may  be  enlarged  by 
filing  back  the  tip  until  the  required  internal  diameter  is  reached. 
To  adjust  the  air  supply  the  wash  bottles  are  filled  with  water  to 
the  depth  of  1  to  lj^  inches  above  the  lower  end  of  inlet  tubes. 
The  jet  pump  is  then  turned  on  to  draw  air  through  the  appa- 
ratus at  a  rapid  rate,  the  battery  circuit  is  closed  to  produce 
a  continuous  spark,  and  the  gas  is  turned  on  last.  This  order 
should  be  followed  every  time  the  burner  is  lighted.  If  the  gas 
is  turned  on  before  both  the  air  flow  and  the  spark  are  started, 
an  explosion  may  result.  As  soon  as  the  gas  has  ignited  the 
battery  circuit  may  be  opened. 

The  amount  of  air  entering  the  burner  tube  must  be  regulated 
rather  carefully,  so  that  the  flame  is  entirely  nonluminous  with  a 
clearly  defined  inner  cone.  The  amount  of  secondary  air  flowing 


ILLUMINATING  GAS  AND  NATURAL  GAS  173 

through  the  apparatus  must,  of  course,  be  sufficient  to  give  com- 
plete combustion.  This  is  assured  when  the  outer  cone  of  the 
flame  is  steady  and  sharply  defined.  If  the  outline  of  the  flame 
appears  " ragged"  or  indistinct,  some  of  the  sulphur  is  certain  to 
escape  oxidation.  There  is  little  danger  of  having  too  much 
secondary  air,  but  the  amount  is  limited  by  the  capacity  of  the 
wash  bottles.  To  insure  complete  absorption  and  prevent  mechan- 
ical loss  of  the  sulphate  solution,  it  is  desirable  to  keep  this  rate 
of  air  flow  reasonably  low,  but  it  is  better  to  use  too  much  air 
than  too  little.  The  primary  air  is  regulated  by  the  pinch  cock  on 
the  inlet  tube,  but  the  adjustment  of  secondary  air  should  be  made 
by  regulating  the  jet  pump  rather  than  by  closing  the  air  inlet. 

When  these  adjustments  have  been  completed  a  test  for  leaks 
should  be  made,  the  gas-supply  line  purged,  and  the  meter  ad- 
justed. While  the  line  is  being  purged  the  soda  lime  tower  is 
filled  and  sufficient  5  per  cent,  solution  of  sodium  carbonate 
(Na2COa),  with  a  few  drops  of  hydrogen  peroxide  or  of  bromine 
water,  is  introduced  into  each  wash  bottle  to  bring  the  liquid 
1  to  lj^  inches  above  the  bottom  of  the  inlet  tube. 

The  burner  is  now  connected  to  the  meter  and  the  meter  read- 
ing recorded.  The  suction,  spark,  and  gas  are  then  turned  on  in 
order,  and  pressure  and  temperature  readings  are  made  and  re- 
corded. The  burner  should  usually  be  adjusted  to  consume  about 
1  cubic  foot  of  gas  per  hour.  When  enough  gas  has  been  burned 
the  gas  is  turned  off  first;  then  the  valve  controlling  the  jet  pump 
is  closed  carefully  to  prevent  tap  water  being  sucked  back  into 
the  wash  bottles.  The  meter,  barometer,  thermometer,  and  mano- 
meter readings  are  again  recorded.  The  contents  of  the  wash 
bottles  are  transferred  to  a  beaker  and  the  bottles  rinsed  twice  with 
a  little  water.  It  is  ordinarily  unnecessary  to  wash  out  the  burner 
chamber  since  it  is  dry  at  all  times  and  the  sulphur  is  mostly 
present  in  the  form  of  sulphur  dioxide,  which  passes  on  quanti- 
tatively. The  hot  walls  prevent  the  condensation  of  any  sulphur 
trioxide  which  may  be  present.  Sulphate  is  determined  in  the 
solution  by  any  of  the  usual  methods.  1  grm.  BaSO4= 0.1373 
grm.  S.  or  2. 1 19  grains  S.  The  result  is  usually  reported  as  grains 
sulphur  per  100  cu.  ft.  of  gas  measured  under  standard  conditions. 

9.  Naphthalene. — The  amount  of  the  hydrocarbon,  naphtha- 
lene CioH8,  usually  present  in  gas  is  less  than  one-tenth  of  1  per 


174  GAS  AND  FUEL  ANALYSIS 

cent.  Its  small  amount  would  make  it  unworthy  of  considera- 
tion were  it  not  for  its  disagreeable  property  of  causing  stoppages 
in  gas  mains.  Its  estimation  is  therefore  sometimes  demanded 
as  one  of  the  steps  in  controlling  the  manufacturing  process. 

The  usual  method  for  purified  gas  is  that  devised  by  Coleman 
and  Smith,1  who  based  their  method  on  Kiister's2  method  for 
separating  naphthalene  from  other  hydrocarbons.  The  method 
depends  upon  the  property  which  naphthalene  possesses  of  com- 
bining molecule  for  molecule  with  picric  acid  to  form  an  insoluble 
compound.  In  the  author's  laboratory  it  has  been  customary 
to  make  the  picric  acid  about  1/20  normal,  which  is  an  almost 
saturated  solution,  and  to  use  as  alkali  Ba(OH)2  1/5  normal, 
with  phenolphthalein,  lacmoid  or  methyl  red  as  indicator.  The 
color  change  is  not  difficult  to  observe,  but  the  same  conditions 
must  always  be  observed  in  the  analyses  that  are  maintained  in 
the  standardization.  When  the  gas  to  be  tested  has  been  puri- 
fied and  there  is  no  danger  of  naphthalene  deposition  at  room 
temperature  the  gas  may  be  passed  through  a  wet  experimental 
meter,  then  through  a  wash  bottle  containing  dilute  tartaric  or 
other  non-volatile  acid  to  remove  all  traces  of  ammonia,  then 
through  a  bottle  containing  water  to  stop  acid  which  might  have 
spattered  over  and  then  through  a  bulbed  gas  washing  tube  with 
about  ten  bulbs  containing  50  c.c.  of  the  standard  picric  acid. 
A  yellow  precipitate  betrays  the  presence  of  naphthalene.  After 
five  or  more  cubic  feet  of  gas  have  been  bubbled  through  the 
apparatus,  the  bulbed  tube  is  disconnected  and  washed  into  an 
Erlenmeyer  flask  of  about  150  c.c.  capacity,  the  bulbed  tube 
being  rinsed  with  50  c.c.  of  picric  acid  from  a  pipette.  The  flask 
is  then  closed  with  a  rubber  stopper  carrying  a  glass  tube  through 
which  most  of  the  air  is  sucked  from  the  flask  by  a  filter  pump  in 
order  that  it  may  not  blow  up  when  heated  later.  The  evacuated 
flask  is  then  placed  in  a  water  bath  which  is  maintained  at  the 
boiling  temperature  for  an  hour.  Rut  ten3  says  that  it  is  sufficient 
to  heat  to  40°  C.  for  half  an  hour.  The  flask  is  then  removed  and 
allowed  to  cool  when  the  naphthalene  picrate  will  have  recrystal- 
lized  as  a  definite  compound  CioH8.  CeHaOHfNC^s.  This  is 


lJour.  of  Gas  Lighting,  75,  798  (1900);  80,  1277  (1902). 

2  Berichte,  27,  1101. 

3  Jour,  fur  Gasbel,  52,  694  (1909). 


ILLUMINATING  GAS  AND  NATURAL  GAS  175 

|  filtered  off  and  an  aliquot  part  of  the  filtrate  is  titrated  with 
alkali.     The  difference  between  the  amount  of  alkali  required 
\  for  this  titration  and  that  which  would  have  been  required  on  a 
,  blank  titration  gives,  when  calculated  for  the  whole  volume  of 
;  picric  acid  present,  the  naphthalene  absorbed.     One  cubic  centi- 
meter of  N/5  Ba(OH)2  is  equivalent  to  0.0256  grm.  naphthalene. 
If  great  accuracy  is  not  required  the  heating  of  the  naphthalene 
picrate  in  its  solution  may  be  dispensed  with. 

When  gas  freed  from  tar  particles  but  otherwise  unpurified 
is  to  be  tested  for  naphthalene,  it  must  be  freed  from  ammonia 
and  hydrogen  sulphide,  which  affect  the  titration.  The  gas 
must  not  be  allowed  to  cool  below  the  temperature  of  the  main 
during  this  purification  process  or  naphthalene  may  deposit. 
The  purifying  train  may  be  placed  in  an  oven  such  as  that  shown 
in  Fig.  40,  placed  so  that  it  is  in  close  proximity  to  the  main 
and  heated  to  the  desired  temperature.  The  first  washer  may 
contain  lead  acetate,  the  second  a  dilute  acid  and  the  third  water. 
The  tube  with  picric  acid  must  not  be  placed  in  the  oven  since 
naphthalene  will  not  be  absorbed  by  a  warm  solution,  but  must 
be  immediately  outside.  If  naphthalene  is  deposited  in  the 
glass  connecting  tube  it  may  be  vaporized  and  driven  forward 
by  heat.  Where  much  naphthalene  is  present  two  bulbed  tubes 
should  be  used  in  series  and  if  much  precipitate  appears  in  the 
second  tube  the  liquid  in  the  first  tube  should  be  renewed  since  a 
dilute  solution  of  picric  acid  does  not  remove  naphthalene  com- 
pletely. The  precipitated  naphthalene  is  estimated  in  the  same 
manner  as  in  the  case  of  purified  gas. 

Where  naphthalene  must  be  estimated  in  crude  gas  containing 
suspended  tar  and  it  is  desired  to  separate  the  naphthalene  pres- 
ent as  vapor  in  the  gas  from  that  which  is  carried  in  the  dissolved 
tar  particles,  the  method  becomes  still  more  complicated.  The 
method  devised  by  the  author1  to  separately  determine  the  naph- 
thalene present  as  vapor  in  the  gas  from  that  which  is  carried  in 
the  dissolved  tar  particles  involves  precipitation  of  naphthalene 
as  the  picrate  with  subsequent  recovery  of  the  naphthalene. 
Considerable  care  is  necessary  in  sampling  gases  which  contain 
tar,  if  it  is  desired  to  distinguish  between  the  naphthalene  actu- 
ally present  as  vapor  in  the  gas  and  that  existing  dissolved  in  the 
lProc.  Mich.  Gas.  Ass.,  1904;  1905,  83.— J.  Gas  Lighting  88,  262  and  92, 
388. 


176 


GAS  AND  FUEL  ANALYSIS 


fine,  mist-like  particles  of  tar  suspended  in  the  gas  and  which  will 
be  removed  later  by  mechanical  scrubbing.  It  is  out  of  the  ques- 
tion to  collect  a  tank  of  gas,  say  from  the  foul  main,  and  transport 
it  to  to  the  laboratory  for  examination.  The  condensation  and 
separation  of  tarry  products  in  the  gas  holder  would  nullify 
the  value  of  the  figures  obtained.  It  is  necessary  to  separate 
the  suspended  tar  and  remove  the  naphthalene  before  change  of 
temperature  has  had  time  to  alter  the  conditions  prevailing 
at  the  point  of  sampling.  This  requires  that  the  tar  vapors 
shall  be  mechanically  filtered  from  the  gas  without  any  change 


Glass  Sleeve  •' 
Covered  with 

Rubber 


FIG.  39.  —  Details  of  naphthalene  train. 


in  temperature.  The  result  is  attained  by  inserting  horizontally 
into  the  main  a  glass  tube  about  J^  in.  in  diameter  filled  with 
glass  wool  or  asbestos  fiber.  This  tube  should  project  into  the 
main  at  least  6  in.  and  at  as  short  a  distance  outside  the  main 
as  possible  should  connect  with  the  picric  acid  absorbing  train, 
and  then  with  a  gas  holder  of  about  1  cu.  ft.  capacity  and  of 
known  volume  as  shown  in  Fig.  2  of  Chapter  I.  The  strong 
solvent  power  of  tar  for  naphthalene  renders  it  absolutely 
essential  that  the  gas  shall  not  be  scrubbed  by  passing  through 
cold  tar,  as  would  be  the  case  if  the  tube  for  separation  of  the 
tar  were  placed  outside  the  main  and,  for  example,  connected 
to  a  pet  cock.  After  the  sample  has  been  drawn,  the  picric 
acid  contains  the  naphthalene  and  tar  which  were  still  present 
in  the  gas  as  vapor.  The  solution  and  precipitate  is  washed 
into  a  200  c.c.  Erlenmeyer  flask  and  treated  with  alkali  to  neu- 


ILLUMINATING  GAS  AND  NATURAL  GAS 


177 


tralize  the  picric  acid.  It  is  our  custom  to  add  here  an  excess 
of  solid  alkali,  making  an  almost  saturated  solution  when  hot, 
merely  to  prevent  so  much  moisture  being  carried  into  the  dry- 
ing tube.  As  this  addition  of  solid  alkali  makes  the  solution  hot, 
it  should  not  be  added  until  just  before  the  apparatus  is  con- 
nected up  so  as  to  avoid  loss  of  naphthalene.  If  the  glass  con- 
necting tube  contains  naphthalene  deposited  from  the  gas  by 
condensation  the  tube  should  be  broken  into  fragments  and 
dropped  into  the  same  flask. 


FIG.  40. — Oven  for  naphthalene  determinations. 

The  flask  is  then  corked  with  a  stopper  carrying  two  glass 
tubes,  one  long  enough  to  reach  nearly  to  the  bottom  of  the 
flask  and  the  other  terminating  just  below  the  cork  and  extending 
above  the  cork  to  make  connections  to  the  tube  containing 
lime  and  phosphorus  pentoxide  as  shown  at  A  of  Fig.  39.  At 
the  other  end  of  the  drying  tube  B  close  connection  is  made  to  a 
small  weighed  U  tube  C  which  can  be  immersed  in  ice  water. 
The  tube  containing  the  asbestos  and  tar  is  connected  directly 
to  a  similar  drying  tube  and  U  tube.  The  arrangement  of  the 
train  is  shown  in  Fig.  39  and  the  whole  set  in  the  oven  is  shown 
in  Fig.  40.  The  oven  is  heated  to  70°-80°  C.  and  air  slowly  drawn 
through  the  system,  volatilizing  the  naphthalene  and  moisture 
in  the  tar.  The  moisture  is  taken  up  by  the  dryer  lime  and 
phosphorus  pentoxide — while  the  naphthalene  passes  on  to  be 
frozen  out  in  the  U  tube  placed  directly  outside  of  the  oven  in  a 

trough  filled  full  of  cracked  ice.     The  analysis  is  complete  when  the 
12 


178  GAS  AND  FUEL  ANALYSIS 

weight  of  the  naphthalene  U  tube  becomes  constant  or 
nearly  so  at  consecutive  weighings  after  a  two-  or  three-hon 
interval.  The  volatilization  of  the  naphthalene  from  the  gas  ii 
usually  complete  in  six  hours.  The  time  required  for  an  analysii 
of  tar  thus  deposited  varies  with  the  amount  of  tar  in  the  sampl< 
and  usually  takes  thirty  or  forty  hours  for  samples  drawn  from  th< 
standpipe  when  the  weight  of  tar  amounts  to  8  or  10  grm 
When  the  analysis  is  complete,  the  tar  volatilizing  tube  is  agaii 
weighed,  the  loss  giving  the  weight  of  moisture  and  naphthalene 
given  off.  Having  the  weight  of  naphthalene  in  the  U  tube,  w( 
have  the  weight  of  moisture  also,  which,  however,  is  at  best  onlj 
approximate,  because  there  is  always  more  or  less  light  oil,  sue! 
as  benzene,  given  off  from  the  tar  with  the  moisture  and  naph 
thalene,  which  cannot  easily  be  estimated.  Finally  the  volatiliz- 
ing tube  is  set  in  a  Soxhlet  extractor  and  the  remaining  content! 
extracted  with  chloroform  until  free  of  all  soluble  material 
After  drying,  the  'tube  is  weighed,  this  giving  the  weight  of  fre< 
carbon  in  the  tar. 

The  oven  used  is  of  galvanized  iron  and  is  20  in.  high  by  16  in 
wide  by  14  in.  deep.  It  is  shown  in  Fig.  40  and  is  arranged  s< 
that  eight  samples  may  be  worked  at  a  time.  The  drying  trail 
consists  of  a  heavy  glass  tube  about  J^  in.  internal  diamete: 
and  12  in.  long.  It  contains  broken  lime  for  about  two-thirds  o 
its  length  and  phosphorus  pentoxide  thoroughly  incorporated  ii 
glass  wool  for  the  other  one-third.  This  introduction  of  the  glasi 
wool  with  the  phosphorus  pentoxide  prevents  the  gas  fron 
forming  channels  in  the  latter  and  thus  aids  in  rendering  the  ex 
traction  of  moisture  complete  before  reaching  the  naphthalene 
U  tube.  The  lime  used  must  be  extremely  rapid  in  its  reactioi 
with  water  in  order  to  avoid  too  great  expense  for  phosphorus 
pentoxide.  It  may  be  readily  made  by  igniting  crushed  lime 
stone  to  a  dull  red  heat  for  two  hours  in  a  muffle.  If  the  lumps  o: 
lime  are  too  small,  the  expansion  attendant  upon  their  slacking 
will  crack  the  tube.  If  the  lumps  are  too  large,  the  gas  will  not  b< 
dried  sufficiently.  A  satisfactory  mixture  is  obtained  by  taking 
everything  that  will  pass  a  four-mesh  sieve  and  will  not  pass  f 
twelve-mesh.  Connection  with  the  naphthalene  U  tube  is  mad( 
as  shown  in  Fig.  39  at  C,  through  a  glass  sleeve  made  air  tight  b} 
a  piece  of  rubber  tubing  placed  over  the  whole.  This  prevents 


ILLUMINATING  GAS  AND  NATURAL  GAS  179 

the  naphthalene  from  coming  in  contact  with  the  rubber.  It  is 
well  known  that  rubber  absorbs  naphthalene.  Nevertheless, 
it  has  been  found  safe  to  use  rubber  stoppers  in  the  volatilizing 
oven.  Rubber  stoppers  in  frequent  use  absorb  all  they  can 
take  up  and  after  a  few  runs  cause  no  further  trouble. 

This  method  allows  the  estimation  of  naphthalene  as  vapor  in 
the  gas,  and  of  water,  non-volatile  tar,  free  carbon  and  naphtha- 
lene in  the  suspended  tar.  The  separation  of  the  water  and  non- 
volatile tar  is  not  very  accurate,  the  light  oils  which  are  vaporized 
by  the  air  drawn  through  being  reported  as  water.  The  estima- 
tion of  naphthalene  is,  however,  quite  accurate.  The  air  passing 
through  will  leave  the  system  saturated  with  naphthalene  at  the 
temperature  of  ice  water,  but  this  loss  need  not  amount  to  over  a 
milligram  for  each  ten  hours  run.  It  is  possible  that  the  naph- 
thalene may  be  contaminated  by  other  hydrocarbons  and  the 
naphthalene  deposit  is  sometimes  slightly  oily  and  has  a  low 
melting  point. 

10.  Ammonia. — Crude  coal  gas  before  scrubbing  may  contain 
as  much  as  three-quarters  of  a  per  cent,  of  NH3  by  volume. 
After  the  gas  has  traversed  the  scrubbers  the  amount  of  ammonia 
should  be  reduced  to  a  trace. 

The  gas  to  be  tested  is  bubbled  through  standard  acid,  suc- 
tion being  produced  by  an  aspirator  holding  a  cubic  foot,  which 
also  acts  as  a  measuring  device.  The  excess  of  acid  is  then 
titrated  back  with  standard  alkali,  cochineal  or  sodium  alizarine 
sulphonate  being  used  as  an  indicator.  If  the  gas  contains,  much 
suspended  tar  the  end  of  the  titration  cannot  be  observed  sharply 
and  it  is  necessary  to  make  the  solution  alkaline  and  redistill 
the  ammonia  into  standard  acid  before  titrating.  One  cubic 
centimeter  of  N/10  acid  equals  0.0017  grm.  NH3. 

11.  Cyanogen. — Cyanogen  compounds  exist  in  small  amounts 
in  unpurified  gas.     In  the  purification  process  they  are  partly 
removed  in  the  ammonia  scrubbers  and  largely  in  the  iron-oxide 
purifiers  or  in  special  scrubbers  containing  compounds  of  iron. 
The  gas  is  estimated  by  bringing  it  into  contact  with  an  alkaline 
solution  carrying  suspended  ferrous  hydroxide  and  titrating  the 
resultant  ferrocyanide.     The  method  according  to  Mueller1  is  as 
follows: 

lProc.  Am.  Gas  Inst.,  5,  249  (1910). 


180  GAS  AND  FUEL  ANALYSIS 

11  To  determine  the  amount  of  cyanogen  in  gas,  the  cyanogen  is 
converted  into  potassium  ferrocyanide  by  passing  the  gas  through  a 
caustic  potash  solution  containing  freshly  precipitated  ferrous  hydrate 
in  suspension.  After  filtering,  the  potassium  ferrocyanide  is  determined 
in  the  clear  solution  by  acidifying  and  titrating  with  a  standard  solution 
of  zinc  sulphate  until  all  ferrocyanide  has  been  precipitated  as  zinc 
ferrocyanide.  The  end  reaction  is  determined  as  follows:  A  drop  of 
a  1  per  cent,  solution  of  ferric  chloride  is  put  on  a  piece  of  white  filter- 
paper  absolutely  free  from  iron.  A  drop  of  the  liquid  being  tested  is 
then  put  on  the  paper  near  the  drop  of  ferric  chloride  so  that  the  liquor 
as  it  spreads  out  on  the  paper  will  come  in  contact  with  the  ferric 
chloride.  Care  must  be  taken  that  the  precipitate  of  zinc  ferrocyanide 
does  not  come  in  contact  with  the  iron  solution.  As  long  as  there  is 
any  ferrocyanide  left  in  solution,  a  blue  color  will  appear  where  the 
two  drops  come  in  contact  due  to  the  formation  of  prussian  blue. 
When  all  ferrocyanide  has  been  precipitated  this  color  will  no  longer 
appear,  which  indicates  the  end  point  of  the  titration.  The  zinc  sul- 
phate solution  is  made  by  dissolving  approximately  5  grm.  of  pure  zinc 
sulphate  in  1  liter  of  water  with  the  addition  of  10  c.c.  of  sulphuric 
acid.  This  solution  is  standardized  with  a  solution  of  10  grm.  of  potas- 
sium ferrocyanide  (K4Fe(CN')6.3H20)  dissolved  in  water  and  diluted 
to  1  liter.  Twenty-five  cubic  centimeters  of  the  potassium  ferrocyanide 
solution  are  put  into  a  beaker  and  titrated  with  the  zinc  sulphate 
solution,  the  end  reaction  being  determined  as  above.  One  cubic 
centimeter  of  the  ferrocyanide  solution  is  equivalent  to  0.0570  grains 
of  cyanogen,  from  which  the  value  of  the  zinc  solution  is  calculated. 

"To  test  for  cyanogen  in  gas  put  15  c.c.  of  a  10  per  cent,  ferrous 
sulphate  (FeS04.7H20)  solution  into  each  of  three  wash-bottles.  Add 
15  c.c.  of  20  per  cent,  caustic  soda  solution  to  each  bottle  and  pass 
about  3  cu.  ft.  of  gas  through  these  bottles  at  the  rate  of  about  1  cu. 
ft.  per  hour.  Rinse  the  contents  of  the  bottles  into  a  beaker,  add  20 
c.c.  more  of  the  caustic  soda  solution  and  heat  to  boiling.  Filter 
and  wash  with  hot  water  until  a  few  drops  of  the  filtrate  no  longer 
show  a  blue  color  when  acidified  and  tested  with  a  drop  of  1  per  cent, 
ferric  chloride  solution.  Transfer  the  filtrate  to  a  500  c.c.  graduated 
flask,  dilute  to  the  mark  and  shake  well.  Take  100  c.c.  of  this  solution 
and  transfer  to  a  beaker  by  means  of  a  pipette.  Slowly  add  dilute  sul- 
phuric acid  (sp.  gr.  about  1.5)  stirring  constantly  until  the  solution 
becomes  slightly  acid  toward  litmus.  Then  run  in  the  zinc  sulphate 
solution  a  few  drops  at  a  time  until  the  drop  test  as  explained  above 
shows  that  the  ferrocyanide  has  all  been  precipitated.  From  the 
amount  of  zinc  sulphate  solution  used  the  amount  of  cyanogen  in  the 
gas  is  calculated." 


ILLUMINATING  GAS  AND  NATURAL  GAS 


181 


12.  Specific  Gravity. — The  simplest  method  of  determining 
the  specific  gravity  of  gases  makes  use  of  the  law  that  different 
gases  streaming  through  a  given  orifice  at  the  same  temperature 
and  pressure  flow  through  the  orifice  at  a  rate  inversely  propor- 
tional to  the  square  root  of  their  specific  gravity.  Since  the  time 
of  flow  is  inversely  proportional  to  the  rate,  the  specific  gravity 
becomes  proportional  to  the  square  of  the 
time  of  flow.  Bunsen  devised  an  inge- 
nious instrument  to  measure  specific  grav- 
ities in  this  way  and  Schilling  later  gave  it 
the  form  which  is  shown  in  Fig.  41.  It 
consists  of  a  glass  cylinder  open  at  the 
bottom  and  fastened  to  a  metal  base  which 
keeps  it  vertical  within  the  larger  cylinder 
of  water.  It  is  closed  at  the  top  by  a  metal 
cap  carrying  two  cocks.  A  is  for  the  in- 
troduction of  the  gas  to  be  tested.  B  is  a 
three-way  cock  which  in  one  position  dis- 
charges the  gas  through  a  side  arm  to  flush 
the  aparatus.  When  this  cock  is  in  the 
vertical  position  the  gas  passes  through  a 
small  opening  in  a  platinum  plate  at  C. 
The  apparatus  should  be  standardized 
against  air  each  time  it  is  used.  The 
calibration  is  made  by  opening  the  air  cock 
and  raising  the  inner  cylinder  until  it  is 
nearly  out  of  water.  It  will  then  be  filled 
with  air.  After  closing  both  cocks  it  is  to 
be  again  lowered  into  the  cylinder  of  water.  The  observer 
opens  the  cock  B  so  that  the  air  streams  out  through  the  capillary 
platinum  opening,  starts  a  stop  watch  as  the  meniscus  passes 
the  lower  mark  on  the  glass  tube  and  stops  the  watch  as  it  passes 
the  upper  mark.  The  instrument  is  now  thoroughly  flushed 
with  gas  and  the  time  required  for  the  volume  of  gas  between 
the  two  calibration  marks  to  stream  out  of  the  opening  is  de- 
termined in  the  same  way.  The  calculation  then  follows  from 
the  formula 

sp.gr.  gas^t2  gas 
sp.  gr,  air     t2  air 


FIG.  41.— Schilling's 
specific  gravity  appa- 
ratus. 


182 


GAS  AND  FUEL  ANALYSIS 


Edwards1  has  made  a  careful  study  of  the  accuracy  of  this 
effusion  method  of  determining  gas  density  and  finds  that  al- 
though the  apparatus  may  serve  well  for  control  work,  errors  of 
ten  per  cent,  in  the  absolute  measurement  are  not  unusual.  If 
calibrated  orifices  are  employed,  better  results  may  be  obtained. 
The  modification  of  apparatus  shown  in  Fig.  42  is  recommended 
for  approximate  work  and  more  elaborate 
models  are  illustrated  where  mercury  is  to  be 
used  as  the  displacing  agent. 

A  more  accurate  determination  of  the 
specific  gravity  of  gas  is  afforded  by  the 
specific  gravity  balance.  Edwards2  has  re- 
viewed the  literature  of  the  subject  and  has 
devised  a  portable  apparatus  capable  of 
giving  the  specific  gravity  with  an  error  of 
less  than  one  part  in  a  thousand.  According 
to  Boyle's  law  the  density  of  a  gas  is  propor- 
tional to  its  pressure;  and  the  buoyant  force 
exerted  upon  a  body  suspended  in  a  gas  is 
proportional  to  the  density  of  the  gas  and, 
therefore,  to  its  pressure.  Hence,  if  the 
buoyant  force  exerted  upon  a  body  is  made 
the  same  when  suspended  successively  in  two 
gases,  then  the  densities  of  the  two  gases  must 
be  the  same  at  these  pressures;  or  the  densities 
of  the  two  gases  at  normal  pressure  are  in 
inverse  ratio  to  the  pressures  when  of  equal  buoyant  force.  The 
Edwards  gas  density  balance  is  illustrated  in  Fig.  43  and  consists 
of  a  balance  beam  B  carrying  a  sealed  cylinder  on  one  end  and  a 
counterweight  on  the  other.  The  balance  beam  with  its  sup- 
port is  mounted  in  a  gas-tight  chamber  to  which  is  attached  a 
mercury  manometer.  In  operation,  the  balance  case  and 
manometer  connections  are  filled  with  dry  air  through  the  inlet  / 
and  the  pressure  adjusted  by  removing  the  excess  gas  through 
the  needle  valve  E  until  the  beam  just  balances,  as  determined 
by  observation  (through  the  adjustable  lens  L)  of  the  cross  line 
on  the  end  of  the  beam.  After  determining  this  pressure,  the 

1  Bureau  of  Standards,  Technologic  Paper  No.  94. 

2  Bureau  of  Standards,  Technologic  Paper  No.  89. 


FIG.  42. — Bureau 
of  Standards  form 
of  simple  specific 
gravity  apparatus. 


ILLUMINATING  GAS  AND  NATURAL  GAS 


183 


balance  is  evacuated  through  E  and  filled  with  the  gas,  the 
pressure  is  then  adjusted  until  the  beam  is  again  in  equilibrium. 
The  specific  gravity  of  the  gas  is  then  the  ratio  of  the  total 
pressure  (manometer  reading  plus  atmospheric  pressure)  required 
to  balance  the  beam  in  air  to  the  total  pressure  required  to 
balance  it  in  the  gas. 


FIG.  43. — Edwards  specific  gravity  balance  for  gases. 

13.  Natural  Gas. — Natural  gas  is  ordinarily  distributed  and 
used  without  any  attempt  at  purification.  There  is,  therefore, 
much  less  call  for  analysis  of  this  product.  The  most  important 
determination  is  that  of  heating  value,  which  is  carried  out  in  a 
gas  calorimeter  as  described  for  illuminating  gas  in  Chapter  VII. 
If  the  burner  of  the  calorimeter  is  adjusted  for  coal  gas  it  will 
have  to  be  readjusted  for  the  natural  gas  and  a  different  tip  may 
have  to  be  inserted.  The  volume  of  the  natural  gas  should  be 
controlled  to  give  about  the  same  rise  in  temperature  in  the  calor- 
imeter as  is  desirable  for  coal  gas.  When  a  knowledge  of  the 
total  sulphur  is  desired  it  is  estimated  by  the  method  of  §  8  of 
this  chapter.  A  few  analyses  of  natural  gas  selected  from  the 
reports  of  the  Bureau  of  Mines  are  given  below.  It  will  be  noted 
that  no  mention  is  made  of  unsaturated  hydrocarbons,  oxygen, 
carbon  monoxide,  or  hydrogen,  which  are  believed  to  be  entirely 
absent  from  American  natural  gas.  The  small  amounts  which 
may  be  found  in  an  ordinary  analysis  are  due  to  air,  absorption 
of  gases  from  water,  solubility  of  the  gas  in  reagents,  or  error 
in  the  explosion  or  combustion  of  the  hydrocarbons.  The  hydro- 
carbons in  the  above  table  are  reported  entirely  as  methane  and 
ethane.  Further  discrimination  is  not  possible  by  ordinary 
methods  of  analysis. 


184 


GAS  AND  FUEL  ANALYSIS 


ANALYSES  OF  NATURAL  GAS: 


Charleston, 
W.  Va. 

Altoona, 
Pa. 

Piqua,  O. 

Los 
Angeles, 
Cal. 

CH4 

76  8 

90  0 

78  3 

59  2 

C2H6  

22  5 

9  0 

12  6 

13  9 

CO2  

0  0 

0  2 

0  2 

26  2 

N2 

0  7 

0  8 

8  9 

0  7 

Calculated  heating  value  at 
60°  F  

1169  0 

1065  0 

1010  0 

841  0 

Calculated  sp.  gr.  air  =  1  ... 

0.67 

0.60 

0.66 

0.88 

*  Burrell  and  Robertson,  Bureau  of  Mines  Technical  Paper  158  (1917). 

The  combustion  of  the  hydrocarbons  of  natural  gas  offers 
considerable  difficulty.  Not  only  is  it  difficult  to  burn  hydro- 
carbons with  copper  oxide  but  Anderson1  states  that  there  is 
difficulty  in  burning  natural  gas  with  oxygen  in  a  combustion 
pipette  if  considerable  amounts  of  gasoline  vapors  are  present. 
In  a  later  article  Anderson2  gives  detailed  corrections  to  be  ap- 
plied to  the  results  of  combustion.  The  effect  of  deviation  from 
the  theoretical  volume  has  been  discussed  in  Chapter  VI.  An- 
derson advocates  the  expression  of  the  results  of  analysis  of 
natural  gas  in  the  form  of  the  average  number  of  carbon  atoms 
per  molecule  of  paraffine  hydrocarbons.  If  n  is  the  average  num- 
ber of  carbon  atoms 

3C02 


2  contraction  — CO2 
The  volume  V  of  paraffine  hydrocarbons  will  then  be 


Corrections  for  deviation  from  theoretical  formulae  are  worked 
out  as  curves  and  formulae  and  corrections  for  calculating  specific 
gravity  and  heating  value  from  analysis  are  also  given  in  the 
paper  referred  to. 

1  /.  Ind.  &  Eng.  Chem.,  9,  142  (1917). 

2  /.  Ind.  &  Eng.  Chem.,  11,  299  (1919). 


ILLUMINATING  GAS  AND  NATURAL  GAS 


185 


Burrell  and  Seibert1  have  developed  a  method  of  analysis  of 
gases  by  fractional  distillation  at  low  temperatures.  A  compari- 
son of  the  results  of  the  application  of  this  method  to  the  analysis 
of  a  Pittsburgh  natural  gas  as  compared  with  the  ordinary  analy- 
sis is  given  below.  It  will  be  noted  that  there  are  material 
differences. 

COMPOSITION  OF  NATURAL  GAS  FROM  PITTSBURGH 


Analysis  by 
ordinary 
methods 

Analysis  by 
fractional  dis- 
tillation at  low 
temperature 

CH4  

79.2 

84.7 

C2H6  

19.6 

9  4 

C3H8 

3  0 

C4Hio  (mainly) 

1  3 

N2  

1.2 

1.6 

14.  Gasoline  in  Natural  Gas. — Some  gases  contain  enough 
gasoline  vapors  to  make  it  pay  to  condense  them  by  compression 
and  refrigeration.  Burrell2  reports  that  the  specific  gravity  of 
the  gas  gives  good  indication  of  its  value  for  this  purpose.  Pitts- 
burgh natural  gas  with  a  specific  gravity  of  0.64  when  compared 
with  air,  does  not  yield  commercial  quantities  of  gasoline.  Gases 
with  specific  gravity  of  0.95  to  1.60  yield  commercially  from  one 
to  five  gallons  of  75  to  98°  Be.  gasoline  per  thousand  cubic  feet  of 
gas.  Heavy  oils  of  various  sorts  may  also  be  used  as  absorbents 
for  gasoline  vapors  and  the  process  may  be  successfully  applied 
to  gases  yielding  less  than  a  pint  of  gasoline  per  1000  cu.  ft.  of 
gas.  Absorption  in  oil  is  also  used  as  an  analytical  method  to 
determine  the  amount  of  gasoline  in  the  gas.  Dykema3  illus- 
trates various  types  of  commercial  testing  apparatus.  A  meas- 
ured quantity  of  gas  is  bubbled  through  a  heavy  petroleum  oil 
preferably  contained  in  a  series  of  washers.  If  only  a  single 
washer  is  used  the  percentage  of  saturation  should  be  kept  be- 

1  J.  Am.  Chem.  Soc.,  36,  1538  (1914). 

2  Bull.  88,  U.  S.  Bureau  of  Mines. 

3  Bureau  of  Mines  Bull.  176.     Recent  developments  in  the  absorption 
process  for  recovering  gasoline  from  natural  gas.     1919. 


186  GAS  AND  FUEL  ANALYSIS 

low  4  per  cent.  In  another  type  of  apparatus  applicable  espe- 
cially to  rich  gases  a  cubic  foot  tank  is  filled  with  the  gas  and 
about  850  cc.  of  absorption  oil  injected  through  one  of  the  valves. 
The  tank  and  contents  are  then  violently  agitated  for  twenty 
minutes  to  make  sure  that  the  oil  has  extracted  all -of  the  gaso- 
line, after  which  the  oil  is  removed  and  800  cc.  of  the  oil  is  dis- 
tilled. In  any  absorption  process  the  amount  of  gasoline  is 
finally  determined  by  distillation  of  the  absorption  oil,  using  a 
condenser  cooled  with  ice  water. 


CHAPTER  XIII 
LIQUID  FUELS 

1.  Introduction. — The   liquid   fuel   most   frequently   used   is 
petroleum  in  either  a  crude  or  semi-refined  form.     Coal  tar  and 
tar  products  rank  next  in  importance.     Alcohol  may  become 
important  in  the  future.     These  fuels,  which  are  to  be  burned 
directly,  are  usually  blown  into  the  furnace  in  a  fine  spray  by 
means  of  steam  or  compressed  air.     The  main  points  to  be  deter- 
mined are  their  heating  value,  their  behavior  hi  the  burner  and 
the  relative  danger  which  attends  their  storage.     Fuels  which 
are  to  be  vaporized  before  combustion,  as  is  the  case  in  internal 
combustion  engines,  kerosene  lamps,  etc.,  require  more  elaborate 
tests. 

2.  Sampling. — The  main  difficulty  in  getting  a  representa- 
tive sample  of  liquid  fuel  is  caused  by  the  layer  of  water  and  sedi- 
ment which  frequently  accumulates  on  the  bottom  of  a  tank  of 
oil  or  on  the  surface  of  one  of  tar.     The  main  portion  of  the  liquid 
may  also  be  stratified  if  various  grades  have  been  mixed.     The 
U.  S.  Bureau  of  Mines1  recommends  that  the  oil  be  sampled  as 
delivered  and  that  either  a  small  stream  be  run  off  continuously 
into  a  drum  from  which,  after  mixing,  a  smaller  sample  shall  be 
taken,  or  that  at  regular  intervals  a  small  dipperful  shall  be  taken 
from  the  main  stream  and  placed  in  a  mixing  drum.    Where  it  is 
necessary  to  sample  from  a  small  tank,  a  proportional  sample  may 
be  obtained  by  slowly  lowering  a  glass  tube  vertically  through  the 
oil  till  the  lower  end  rests  on  the  bottom.     If  now  the  upper 
end  be  closed  by  the  thumb  a  column  of  liquid  may  be  drawn 
out  which  represents  the  composition  of  the  vertical  section  at 
the  point  of  sampling.     For  large  tanks  the  glass  tube  is  replaced 
by  one  of  tin  carrying  throughout  its  length  a  stiff  wire  on  whose 
lower  end  is  a  tapering  cork.     When  the  cork  hits  the  bottom 

1  Technical  Paper  3,  Bureau  of  Mines.  Specifications  for  the  Purchase  of 
Fuel  Oil  for  the  Government  with  Directions  for  Sampling  Oil  and  Natural 
Gas. 

187 


188  GAS  AND  FUEL  ANALYSIS 

of  the  tank  as  the  tube  is  lowered,  it  is  forced  up  into  the  tube, 
sealing  the  latter  so  that  the  sample  may  be  drawn  to  the  surface 
without  leakage.  In  default  of  a  sampling  tube  a  corked  empty 
bottle  with  a  string  tied  to  the  cork  may  be  lashed  to  a  stick 
and  be  used.  When  the  bottle  has  been  lowered  to  the  desired 
depth  a  pull  on  the  string  removes  the  cork  and  allows  the  bottle 
to  fill  with  oil  which  can  be  withdrawn  and  form  part  of  a  com- 
posite sample. 

3.  Heating  Value. — The  heating  value  of  liquid  fuels  may  be 
determined  in  either  the  bomb  or  Parr  calorimeter  in  accordance 
with  the  general  directions  in  Chapters  XVI  and  XVII.  Some 
difficulty  in  combustion  will  be  experienced  since  all  the  com- 
pounds volatilize  very  rapidly  during  combustion  and  there  is 
danger  that  some  of  the  vapors  may  break  through  the  flame 
zone  without  being  completely  burned.  Incomplete  combustion 
may  usually  be  detected  on  opening  the  calorimeter  by  the  odor, 
and  the  presence  of  soot  on  the  inside  of  the  cover.  The  difficulty 
becomes  greater  with  volatile  liquids  like  gasoline  or  alcohol,  both 
because  of  their  greater  volatility  in  the  calorimeter  and  because 
of  the  difficulty  of  weighing  the  sample  accurately. 

Slightly  volatile  liquids  such  as  tar  and  heavy  petroleum  oils 
may  be  weighed  directly  into  the  capsule  of  the  bomb  calorimeter 
and  burned  completely,  if  oxygen  under  25  atmospheres  pressure 
is  used.  It  is  advisable  to  place  on  the  oil  a  small  weighed  pellet 
of  sugar  or  benzoic  acid  to  start  combustion.  More  volatile 
liquids  must  be  weighed  in  thin- walled  bulbs  of  about  0.5  c.c. 
capacity  with  capillary  necks  which  the  analyst  may  blow  for 
himself  out  of  fine  glass  tubing.  These  are  filled  by  warming 
the  weighed  bulb  and  immersing  the  open  neck  in  the  liquid. 
Contraction  of  the  air  in  the  bulb  draws  up  a  little  of  the  liquid 
and  by  repetition  of  the  process  the  bulb  may  be  filled.  The  capil- 
lary neck  may  then  be  sealed  close  to  the  bulb  with  a  small  blow- 
pipe flame.  The  increase  in  weight  of  the  bulb  plus  the  portion 
of  the  neck  fused  off  gives  the  weight  of  oil  in  the  sample.  The 
sealed  bulb  is  placed  on  the  capsule  of  the  calorimeter  and  around 
it  is  piled  about  0.25  grm.  of  sugar  or  benzoic  acid  in  contact  with 
the  fuse  wire.  The  combustion  of  this  material  breaks  the  bulb 
and  ignites  the  contents.  Richards  and  Jesse1  have  shown  that 
1  Jour.  Am.  Chem.  Soc.,  32,  268  (1910). 


LIQUID  FUELS  189 

. 

even  this  method  fails  to  give  complete  combustion  with  volatile 
liquids  like  benzene.  They  recommend  the  following  procedure 
as  successful. 

"The  benzene  in  a  very  thin  glass  bulb  was  placed  in  the  bottom  of 
a  narrow  platinum  crucible,  2  cm.  in  diameter  and  2.5  cm.  high.  A  few 
millimeters  above  the  bulb  was  fixed  a  small  platform  of  thin  glass 
bearing  a  weighed  quantity  of  powdered  sugar.  The  passage  of  a  cur- 
rent through  the  coil  of  iron  wire  ignited  the  sugar,  which  in  its  turn 
burst  the  bulb  and  ignited  the  benzene  at  a  moment  when  the  whole 
top  of  the  narrow  crucible  was  filled  with  flame  from  the  burning  sugar. 
Thus  none  of  the  benzene  vapor  could  escape  ignition.  The  trouble 
with  the  old  method  had  been  that  the  larger  crucible  was  too  wide. 
Moreover,  the  sugar  had  been  beneath  the  benzene  instead  of  above 
it,  so  that  some  of  the  benzene  escaped  unconsumed.  The  amount 
which  thus  escaped  was  greater  when  there  was  more  nitrogen  present 
than  when  there  was  less.  Obviously,  with  non-volatile  compounds 
like  sugar  the  width  of  the  crucible  would  make  no  difference." 

Gelatine  capsules  such  as  used  by  pharmacists  have  also  been 
recommended  as  containers  for  volatile  oils,  but  their  moisture 
content  changes  so  rapidly  in  the  air  that  it  is  difficult  to  keep 
constant  the  necessary  correction  factor  for  the  gelatine. 

The  heating  value  of  oils  may  also  be  determined  in  the  Parr 
calorimeter,  which  is  described  in  Chapter  XVII.  Non-volatile 
oils  may  be  weighed  directly  into  the  calorimeter  which  already 
contains  the  peroxide  mixture,  and  mixed  thoroughly  with  the 
charge  by  means  of  a  stiff  wire.  Volatile  liquids  may  be  placed  in 
the  calorimeter  in  a  thin-walled  glass  bulb  as  directed  for  the 
bomb  calorimeter,  and  the  charge  of  chemicals  placed  upon  it. 
The  calorimeter  is  then  closed  with  the  cap  provided  and  shaken 
violently  until  the  bulb  is  broken  and  the  oil  is  mixed  with  the 
peroxide.  A  correction  in  addition  to  those  specified  in  Chapter 
XVII  must  be  deducted  for  the  heat  liberated  by  reaction  between 
the  peroxide  and  the  glass  of  the  bulb.  Professor  Parr  gives 
this  correction  as  0.017°  C.  per  0.1  grm.  glass. 

The  weight  of  oil  taken  should  be  about  0.3  grm.  and  the  charge 
10  grm.  of  Na202  and  1  grm.  of  KC1O3.  The  use  of  0.2  grm. 
benzoic  acid  is  also  advantageous.  Care  must  be  taken  that  crude 
petroleum  and  tars  do  not  carry  much  emulsified  water,  for  the 
water  reacts  with  the  peroxide  with  evolution  of  heat.  In  ex- 


190 


GAS  AND  FUEL  ANALYSIS 


treme  cases  a  violent  explosion  may  take  place,  wrecking  the 
calorimeter. 

If  the  oil  is  of  such  a  type  that  it  may  be  burned  without  smoke 
in  a  burner  without  a  wick  and  there  is  at  least  a  pint  of  the  oil 
available,  the  most  convenient  method  of  determining  heat 
value  is  in  a  calorimeter  of  the  type  whose  use  for  determining 
the  heating  value  of  gases  is  described  in  Chapter  VII.  The 
apparatus  as  modified  for  liquids  requires  a  suitable  burner  for 
the  oil  which  hangs  upon  a  balance  during  the  determination  as 


FIG.  44. — Calorimeter  for  heating  value  of  oils. 

shown  in  Fig.  44.  The  lamp  as  shown  in  the  illustration  requires 
150-200  c.c.  of  oil.  To  start  the  lamp  the  cup  L  is  filled  with 
alcohol  which  is  lighted  to  preheat  the  burner  head,  n.  When  the 
alcohol  is  nearly  burned  away,  air-pressure  is  placed  upon  the 
liquid  by  a  hand  pump  connected  to  m.  The  oil  rises  in  the  bur- 
ner, vaporizes  and  ignites  in  the  alcohol  flame.  The  pumping  is 
continued  until  a  freely-burning  blue  flame  results  when  the  pump 
is  disconnected.  After  the  water  is  flowing  normally  through  the 
calorimeter,  the  lighted  lamp  is  inserted  and  centered  in  the  com- 
bustion space.  When  equilibrium  has  been  reached,  the  balance 
12 


LIQUID  FUELS  191 

is  brought  to  zero  by  proper  adjustment  of  weights  in  the  pan 
and  the  experiment  started.  After  a  definite  weight  of  oil, 
usually  5  or  10  grm.,  has  been  burned,  the  experiment  is  inter- 
rupted and  from  the  rise  in  temperature  and  the  weight  of 
water  heated  the  heating  value  of  the  fuel  may  be  calculated. 
The  details  and  precautions  are  in  general  the  same  as  given  for 
the  gas  in  Chapter  VII.  Especial  care  must  be  taken  that  the 
flame  does  not  impinge  directly  against  the  metal  of  the  calor- 
imeter since  incomplete  combustion  will  result  from  the  sudden 
cooling  of  the  gases  while  combustion  is  still  in  progress. 

4.  Specific  Gravity. — The  specific  gravity  of  petroleum  products 
,is  less  than  1  and  is  usually  reported  on  the   Baume  scale 
f  for  liquids  lighter  than  water.     Tar  is  usually  heavier  than 

water  and  its  specific  gravity  is  reported  directly.  If  a  sufficient 
quantity  of  material  is  available  and  it  is  not  too  viscous,  the 
specific  gravity  may  be  determined  with  approximate  accuracy 
by  a  hydrometer  spindle.  If  greater  accuracy  is  required  or 
if  only  a  small  sample  is  available  a  pycnometer  or  Westphal 
balance  must  be  used.  If  a  specific  gravity  on  water-free  material 
is  demanded,  the  oil  must  be  put  into  a  flask  without  the  addition 
of  any  diluent  and  distilled  slowly  till  the  water  is  off.  The 
oil  distilled  is  then  separated  from  the  water  and  returned  to 
the  residue  in  the  still  after  it  has  cooled.  A  comparison  of  the 
Baume*  scale  for  liquids  lighter  than  water  and  the  corresponding 
specific  gravities  is  given  in  Table  XIII  of  the  Appendix. 

5.  Moisture. — The   various   methods   for  the   determination 
of  water  hi  petroleum  have  been  carefully  examined  by  Allen 
and  Jacobs.1    They  recommend  a  method  which  involves  the 
measurement  of  the  hydrogen  evolved   by  the   action  of  the 
water  on  metallic  sodium  and  also  the  method  of  distillation, 
either  with  or  without  the  addition  of  water-saturated  toluene 
or  xylene.     The  latter  method  will  probably  give  the   better 
results  in  inexperienced  hands.     It  may  be  used  for  tar  as 
well  as  petroleum  products.     The  toluene  is  added  to  diminish 
the  viscosity  of  the  mass  and  lessen  the  danger  of  foaming 
and  bumping.     Instead  of  toluene,  xylene  or  petroleum  benzine 
with  a  boiling-point  of  110  to  150°  C.  may  be  used.     The  diluent 
must,  however,  be  first  shaken  with  water  and  then  allowed 
to  stand  until  perfectly  clear  in  order  that  it  may  not  dissolve 

technical  Paper  25,  U.  S.  Bureau  of  Mines,  1912. 


192  GAS  AND  FUEL  ANALYSIS 

any  of  the  water  of  the  sample.  The  sample  of  about  100 
grin,  is  weighed  into  a  distilling  flask  holding  at  least  500  c.c. 
and  to  it  is  added  a  roughly  measured  volume  of  100  c.c.  of 
the  diluent,  or  200  c.c.  if  the  sample  is  very  viscous.  The 
distillation  is  started  slowly  and  continued  until  the  distillate 
no  longer  comes  over  turbid  and  approximately  as  much  oil 
has  distilled  as  was  added  as  a  diluent.  The  distillate  is  caught 
in  a  graduated  cylinder  and  the  volume  of  water  read  directly 
after  sufficient  time  has  been  given  for  it  to  settle  by  gravity. 
Allen  and  Jacobs  state  that  the  method  may  be  made  accurate  to 
approximately  0.033  grm.  water  for  each  100  c.c.  of  benzene  and 
oil  in  the  distillate. 

The  details  of  a  similar  method  for  the  determination  of 
water  in  tar  as  used  in  the  laboratories  of  the  Barret  Manufac- 
turing Company  have  been  published  by  S.  R.  Church.1  He 
specifies  exactly  the  dimensions  of  the  still,  the  manner  of 
placing  the  thermometer  and  other  details.  The  distillation 
is  to  be  continued  until  the  thermometer  in  the  vapor  has 
reached  205°  C.  He  recommends  a  convenient  form  of  graduated 
separatory  funnel  for  the  distillate  and  states  that  a  clean 
separation  of  the  oil  and  water  can  be  obtained  if  25  c.c.  of 
benzene  is  introduced  into  the  separatory  funnel  before  the 
distillation  is  started. 

6.  Proximate  Analysis. — A  proximate  analysis  in  the  sense 
in  which  it  is  used  in  coal  analysis  is  not  often  made  on  liquid 
fuels  because  they  are  so  largely  volatile  that   the   test  has 
little   meaning.     The   ash   gives   some   measure   of   suspended 
earthy  solids  and  in  the  case  of  tar,  the  fixed  carbon  gives  an 
indication  of  the  amount  of  "free  carbon"   in  the  tar.     It  is 
necessary  to  modify  the  standard  method  for  volatile  matter  in 
coal  by  heating  the  crucible  gently  until  all  foaming  has  stopped. 

7.  Suspended  Solids. — Suspended  solids  which  in  the  case 
of  crude  petroleums  usually  are  earthy  matters  and  in  the 
case  of  tars  are  fine  particles  of  coke  forming  the  so-called 
"free  carbon"  are  separated  by  filtration  and  washing.     The 
oil  or  tar  is  first  filtered  through  a  30-  or  40-mesh  sieve  to  remove 
coarse  foreign  bodies  accidentally  included.     A  weighed  sample 
of  5  or  10  grm.  is  then  diluted  with  pure  benzene  or  toluene 
until  it  will  filter  readily.    The  solution  is  filtered  through  a 

*  Jour,  Ind.  and  Eng.  Chem,.  3,  228  (1911). 


LIQUID  FUELS 


193 


pair  of  weighed  heavy  filter  papers  or  through  a  Gooch  funnel 
and  the  filter  washed  with  more  of  the  warm  solvent  until  the 
extraction  is  complete.  The  filter  is  then  dried  at  105°  C. 
The  increase  in  weight  gives  suspended  solids.  If  there  is 
much 'water  in  the  liquid  being  examined  it  may  be  retained 
on  the  filter  in  the  form  of  drops  during  the  first  filtration. 
This  water  may  be  driven  off  by 
gentle  heating  and  the  extraction 
of  soluble  material  then  continued. 
8.  Flash  Point.— The  flash  point 
of  an  oil  indicates  the  temperature 
at  which  the  oil  gives  off  com- 
bustible vapors  with  sufficient 
rapidity  to  form  an  explosive  mix- 
ture with  the  air  above  it.  The 
flash  point  will  depend  upon  the 
rate  of  heating  the  oil,  the  volume 
of  air  above  it,  the  rapidity  with 
which  the  air  is  replaced  and 
many  other  variables.  It  is  evi- 
dent that  the  conditions  must  be 
closely  specified  in  order  that  the 
results  may  be  of  value.  The 
figure  is  of  great  importance  with 
kerosene  oil  and  most  of  the  states 
have  definite  and  for  the  most  part 
different  regulations  on  the  subject. 
The  older  forms  of  apparatus  had 
open  cups,  but  the  more  modern  FlG  45._Tag  ciosed  tester  for 
forms  have  closed  cups.  The  flash  point  of  oils. 

American  Society  for  Testing  Ma- 
terials   has   adopted    as   its   standard   the  Tag  Closed  Tester 
illustrated  in  Fig.  45.     The  United  States  Fuel  Administration 
has  adopted  the  same  instrument  for  testing  the  flash-point  of 
kerosene.     The  method  of  determining  flash  point  is  as  follows:1 

1.  (a)  Flash  point  shall  be  determined  with  the  Tag  Closed  Tester, 
operated  in  accordance  with  the  directions  given  below. 

1  Proceedings  Am.  Soc.  Test.  Mat.,  18,  685  (1918). 

13 


194  GAS  AND  FUEL  ANALYSIS 

(b)  For  unofficial  tests  any  suitable  closed  type  of  tester  such  as  the 
Abel,  the  Abel-Pensky  or  the  Elliott  may  be  used. 

2.  (a)  If  gas  is  available,  connect  a  ^-in.  rubber  tube  to  the  corru- 
gated gas  connection  on  the  oil  cup  cover.     If  no  gas  is  available,  un- 
screw the  test  flame  burner-tip  from  the  oil  chamber  on  the  cover,  and 
insert  a  wick  of  cotton  cord  in  the  burner-tip  and  replace  it.     Put  a 
small  quantity  of  cotton  waste  in  the  oil  chamber,  and  insert  a  small 
quantity  of  signal,  sperm  or  lard  oil  in  the  chamber,  light  the  wick  and 
adjust  the  flame,  so  that  it  is  exactly  the  size  of  the  small  white  bead 
mounted  on  the  top  of  the  tester. 

(6)  The  test  shall  be  performed  in  a  dim  light  so  as  to  see  the  flash 
plainly. 

(c)  Surround  the  tester  on  three  sides  with  an  inclosure  to  keep  away 
draughts.     A  shield  about  18  in.  square  and  2  ft.  high,  open  in  front, 
is  satisfactory,  but  any  safe  precaution  against  all  possible  room  draughts 
is  acceptable.     Tests  made  in  a  laboratory  hood  or  near  ventilators  will 
give  unreliable  results. 

(d)  See  that  the  tester  sets  firm  and  level. 

(e)  For  accuracy,  the  flash-point  thermometers  which  are  especially 
designed  for  the  instrument  should  be  used,  as  the  position  of  the  bulb 
of  the  thermometer  in  the  oil  cup  is  essential. 

3.  Put  the  water-bath  thermometers  which  are  especially  designed  for 
the  instrument  in  place,  and  place  a  receptacle  under  the  overflow  spout 
to  catch  the  overflow.     Fill  the  water  bath  with  water  at  such  a  temper- 
ature that,  when  testing  is  started,  the  temperature  of  the  water  bath 
will  be  at  least  10°  C.  below  the  probable  flash  point  of  the  oil  to  be  tested. 

4.  Put  the  oil  cup  in  place  in  the  water  bath.     Measure  50  c.c.  of 
the  oil  to  be  tested  in  a  pipette  or  a  graduate,  and  place  in  the  oil  cup. 
The  temperature  of  the  oil  shall  be  at  least  10°  C.  below  its  probable 
flash  point  when  testing  is  started.     Destroy  any  bubbles  on  the  surface 
of  the  oil.     Put  on  the  cover,  with  flash-point  thermometer  in  place 
and  gas  tube  attached.    Light  the  pilot  light  on  the  cover  and  adjust 
the  flame  to  the  size  of  the  small  white  bead  on  the  cover. 

5.  Light  and  place  the  heating  lamp,  filled  with  alcohol,  in  the  base 
of  the  tester  and  see  that  it  is  centrally  located.     Adjust  the  flame  of 
the  alcohol  lamp  so  that  the  temperature  of  the  oil  in  the  cup  rises  at 
the  rate  of  about  1°  C.  per  minute,  not  faster  than  1.1°  nor  slower 
than  0.9°  per  minute. 

6.  (a)  Record  the  barometric  pressure  which,  in  the  absence  of  a 
laboratory  instrument,  may  be  obtained  from  the  nearest  Weather 
Bureau  Station. 

(b)  Record  the  temperature  of  the  oil  sample  at  start. 

(c)  When  the  temperature  of  the  oil  reaches  about  5°  C.  below  the 


LIQUID  FUELS  195 

probable  flash  point  of  the  oil,  turn  the  knob  on  the  cover  so  as  to  intro- 
duce the  test  flame  into  the  cup,  and  turn  it  promptly  back  again.  Do 
not  let  it  snap  back.  The  time  consumed  in  turning  the  knob  down 
and  back  should  be  about  one  full  second,  or  the  time  required  to  pro- 
nounce distinctly  the  words  "one-thousand-and-one." 

(d)  Record  the  time  of  making  the  first  introduction  of  the  test  flame. 

(e)  Record  the  temperature  of  the  oil  sample  at  the  time  of  the  first 
test. 

(/)  Repeat  the  application  of  the  test  flame  at  every  0.5°  C.  rise  in 
temperature  of  the  oil  until  there  is  a  flash  of  the  oil  within  the  cup. 
Do  not  be  misled  by  an  enlargement  of  the  test  flame  or  halo  around 
it  when  entered  into  the  cup,  or  by  slight  flickering  of  the  flame;  the 
true  flash  consumes  the  gas  in  the  top  of  the  cup  and  causes  a  very  slight 
explosion. 

(g]  Record  the  time  at  which  the  flash  point  is  reached. 

(h)  Record  .the  flash  point. 

(i)  If  the  rise  in  temperature  of  the  oil,  from  the  "time  of  making 
the  first  introduction  of  the  test  flame"  to  the  "time  at  which  the  flash 
point  is  reached"  was  faster  than  1.1°  or  slower  than  0.9°  C.  per  minute 
the  test  should  be  questioned,  and  the  alcohol  heating  lamp  adjusted 
so  as  to  correct  the-  rate  of  heating.  It  will  be  found  that  the  wick  of 
this  lamp  can  be  so  accurately  adjusted  as  to  give  a  uniform  rate  of 
rise  in  temperature  of  1°  C.  per  minute  and  remain  so. 

7.  (a)  It  is  not  necessary  to  turn  off  the  test  flame  with  the  small 
regulating  valve  on  the  cover;  leave  it  adjusted  to  give  the  proper  size 
of  flame. 

(b)  Having  completed  the  preliminary  test,  remove  the  heating  lamp, 
lift  up  the  oil  cup  cover,  and  wipe  off  the  thermometer  bulb.     Lift  out 
the  oil  cup,  and  empty  and  carefully  wipe  it.     Throw  away  all  oil 
samples  after  once  used  in  making  a  test. 

(c)  Pour  cold  water  into  the  water  bath,  allowing  it  to  overflow  into 
a  receptacle,  until  the  temperature  of  the  water  in  the  bath  is  lowered 
to  8°  C.  below  the  flash  point  of  the  oil,  as  shown  by  the  previous  test. 

With  cold  water  of  nearly  constant  temperature,  it  will  be  found 
that  a  uniform  amount  will  be  required  to  reduce  the  temperature  of 
the  water  bath  to  the  required  point. 

(d)  Place  the  oil  cup  back  in  the  bath  and  measure  into  it  a  50-c.c. 
charge  of  fresh  oil.     Destroy  any  bubbles  on  the  surface  of  the  oil, 
put  on  the  cover  with  its  thermometer,  put  in  the  heating  lamp,  record 
the  temperature  of  the  oil,  and  proceed  to  repeat  the  test  as  described 
above  in  Sections  4  to  6,  inclusive.     Introduce  the  test  flame  for  first 
time  at  a  temperature  of  5°  C.  below  the  flash  point  obtained  on  the 
previous  test. 


196 


GAS  AND  FUEL  ANALYSIS 


8.  If  two  or  more  determinations  agree  within  0.5°  C.,  the  average 
of  these  results,  corrected  for  barometric  pressure,  shall  be  considered 
the  flash  point.     If  two  determinations  do  not  check  within  0.5°  C.,  a 
third  determination  shall  be  made  and  if  the  maximum  variation  of 
the  three  tests  is  not  greater  than  1°  C.,  their  average,  after  correcting 
for  barometric  pressure,  shall  be  considered  the  flash  point. 

9.  A  correction  table  furnished  with  each  instrument,  for  converting 
the  results  of  tests  made  at  varying  barometric  pressures  to  equivalent 
temperatures  at  the  standard  barometric  pressure  of  760  mm. 

9.  Gasoline. — Gasoline  is  defined  in  Webster's  new  Inter- 
national Dictionary  as  "a  volatile  inflammable  liquid  used  as  a 
solvent  for  oils,  fats,  etc.,  as  a  carburetant,  and  to  produce  heat 
and  motive  power."  The  gasoline  of  commerce  has  changed  its 
composition  markedly  within  recent  years.  Originally  one  of 
the  volatile  fractions  obtained  by  "straight"  distillation  of 
petroleum,  it  has  changed  to  be  largely  a  product  of  destructive 
distillation  with  progressively  lower  Baum£  gravity  and  higher 
average  boiling  point.  Rather  heavy  oils  are  made  to  flash 
more  readily  through  mixture  with  the  very  volatile  casing-head 
gasolines  recovered  from  natural  gas.  The  definition  given 
above  is  broad  enough  to  cover  benzene,  and  other  products 
derived  from  destructive  distillation  of  coal,  as  well  as  alcohol 
and  other  products  from  destructive  distillation  of  wood  or  fer- 
mentation of  grain  or  molasses. 

It  is  obvious  that  with  such  a  wide  range  of  chemical  composi- 
tion, only  the  broadest  tests  can  be  applied.  The  determination 
of  flash  point  is  unnecessary  because  all  gasolines  flash  at  ordi- 
nary temperatures.  Heating  value  is  of  some  importance  with 
the  mixed  products  for,  as  shown  by  Table  IX  of  the  Appendix, 
the  heating  values  may  vary  widely.  The  following  figures  will 
illustrate  this: 

HEATING  VALUE  OF  LIQUID  FUELS 


Name 

Formula 

Sp.  gr. 

Heating  value 

Per  pound 

Per  gallon 

Pentane  

CsHi2 
CeHi4 
C6H6 
GH3OH 

C,HROH 

0.6273 
0.6640 
0.8846 
0.8027 
0.7946 

21,177 
20,914 
18,447 
10,250 
13.325 

110,670 
115,620 
135,950 
68,540 
88.200 

Hexane  

Benzene 

Methyl  alcohol  
Ethvl  alcohol.. 

LIQUID  FUELS  197 

Since  liquid  fuels  are  usually  sold  by  volume  it  is  the  heat 
units  in  a  gallon  which  are  important.  On  this  basis  benzene  is 
seen  to  be  distinctly  the  best  and  methyl  alcohol  the  poorest. 
However,  other  considerations  than  heating  value  enter  into  the 
efficiency  with  which  these  fuels  are  used  in  an  internal  combus- 
tion engine.  Benzene  with  its  high  carbon  content  tends  to 
form  free  carbon  in  the  engine  cylinder  which  cuts  down  its 
efficiency.  Alcohol  with  its  higher  oxygen  content  is  free  from 
this  trouble  and  in  admixture  with  hydrocarbons  lessens  forma- 
tion of  free  carbon.  Methyl  and  ethyl  alcohol  may  both  be 
used  with  higher  compressions  than  gasoline  without  preignition, 
so  that  a  gallon  of  ethyl  alcohol  is,  in  a  suitably  designed  engine, 
practically  the  equivalent  of  a  gallon  of  gasoline.  The  best  test 
of  a  motor  spirit  is  an  actual  operating  test  in  an  engine  similar 
to  that  in  which  it  is  to  be  used.  The  distillation  test  is  the 
best  laboratory  guide  in  predicting  how  an  oil  will  behave  in 
the  carburetor  and  cylinder. 

10.  Specifications  for  Motor  Gasoline. — The  committee  on 
Standardization  of  Petroleum  Specifications  appointed  by  the 
United  States  Fuel  Administration  has  adopted  specifications 
effective  November  25,  1919,  of  which  the  following  is  a  copy. 

Quality. — Gasoline  to  be  high  grade,  refined,  and  free  from  water  and 
all  impurities,  and  shall  have  a  vapor  tension  not  greater  than  ten  pounds 
per  square  inch  at  100°  F.  temperature,  same  to  be  determined  in  ac- 
cordance with  the  current  "Rules  and  Regulations  for  the  transporta- 
tion of  explosives  and  other  dangerous  articles  by  freight,"  as  issued  by 
the  Interstate  Commerce  Commission. 

Inspection. — Before  acceptance  the  gasoline  will  be  inspected.  Sam- 
ples of  each  lot  will  be  taken  at  random.  These  samples  immediately 
after  drawing  will  be  retained  in  a  clean,  absolutely  tight  closed  vessel 
and  a  sample  for  test  taken  from  the  mixture  in  this  vessel  directly 
into  the  test  vessel. 

Specifications. — (a)  Boiling  point  must  not  be  higher  than  60°  C. 
(140°  F.). 

(6)  20  per  cent,  of  the  sample  must  distill  below  105°  C.  (221°  F.). 

(c)   50  per  cent,  must  distill  below  140°  C.  (284°  F.). 

(«0  90  per  cent,  must  distill  below  190°  C.  (374°  F.). 

(e)  The  end  or  dry  point  of  distillation  must  not  be  higher  than 
225°  C.  (437°  F.). 


198 


GAS  AND  FUEL  ANALYSIS 


(/)  Not  less  than  95  per  cent,  of  the  liquid  will  be  recovered  in  the 
receiver  from  the  distillation. 

Test. — One  hundred  cubic  centimeters  will  be  taken  as  a  test  sample. 
The  apparatus  and  method  of  conducting  the  distillation  test  shall  be 
that  adopted  by  Sub-Committee  XI  of  Committee  D-l  of  the  American 
Society  for  Testing  Materials1  (as  shown  in  Fig.  46),  with  the  following 
modifications : 


FIG.  46. — Apparatus  for  distillation  of  petroleum. 

First:  The  temperature  shall  be  read  against  fixed  percentage  points, 
and,  second:  the  thermometer  shall  be  as  hereinafter  described: 

Flask. — The  flask  used  shall  be  the  standard  100  c.c.  Engler  Flask, 
described  in  the  various  textbooks  on  petroleum.  Dimensions  are  as 
follows: 

Dimensions  Cm. 

Outside  diameter  of  bulb 6.5 

Outside  diameter  of  neck 1.6 


Length  of  neck 15 . 0 

Length  of  vapor  tube 10 . 0 

Outside  Diameter  of  vapor  tube 0.6 


Inches 
2.56 
0.63 
5.91 
3.94 
0.24 


1  American  Society  for  Testing  Materials,  Year  Book  for  1915,  pp.  568- 
569;  or  pt.  1,  Committee  Reports,  1916,  vol.  16,  pp.  518-521.  See  alsc 
Bureau  of  Mines  Technical  Papers  Nos.  166  and  214. 


LIQUID  FUELS  199 

Position  of  vapor  tube,  9  cm.  (3.55  in.)  above  the  surface  of  the  gaso- 
line when  the  flask  contains  its  charge  of  100  c.c.  The  tube  is  approxi- 
mately in  the  middle  of  the  neck.  The  observance  of  the  prescribed 
dimensions  is  considered  essential  to  the  attainment  of  uniformity  of 
results. 

The  flask  shall  be  supported  on  a  ring  of  asbestos  having  a  circular 
opening  \Y±  in.  in  diameter;  this  means  that  only  this  limited  portion 
of  the  flask  is  to  be  heated.  The  use  of  wire  gauze  is  forbidden. 

Condenser. — The  condenser  shall  consist  of  a  thin  walled  tube  of 
metal  (brass  or  copper)  K  in.  internal  diameter  and  22  in.  long.  It 
shall  be  set  at  an  angle  of  75°  from  the  perpendicular  and  shall  be  sur- 
rounded with  a  cooling  jacket  of  the  trough  type.  The  lower  end  of 
the  condenser  shall  be  cut  off  at  an  acute  angle  and  shall  be  curved  down 
for  a  length  of  3  inches.  The  condenser  jacket  shall  be  15  in.  long. 

Thermometer. — The  thermometer  shall  be  made  of  selected  enamel- 
backed  tubing  having  a  diameter  between  5.5  and  7  mm.  The  bulb 
shall  be  of  Jena  normal  or  Corning  normal  glass,  its  diameter  shall  be 
less  than  that  of  the  stem  and  its  length  between  10  and  15  mm.  The 
total  length  of  the  thermometer  shall  be  approximately  380  mm.  The 
range  shall  cover  0°  C.  (32°  F.)  to  270°  C.  (518°  F.)  with  the  length  of 
the  graduated  portion  between  the  limits  of  210  to  250  mm.  The  point 
marking  a  temperature  of  35°  C.  (95°  F.)  shall  not  be  less  than  100  inm. 
nor  more  than  120  mm.  from  the  top  of  the  bulb.  For  commercial 
use  the  thermometer  may  be  graduated  in  the  Fahrenheit  scale. 

The  scale  shall  be  graduated  for  total  immersion.  The  accuracy 
must  be  within  about  0.5°  C.  The  space  above  the  meniscus  must  be 
filled  with  an  inert  gas,  such  as  nitrogen,  and  the  stem  and  bulb  must 
be  thoroughly  aged  and  annealed  before  being  graduated. 

Source  of  Heat  in  Gasoline  Distillation. — The  source  of  heat  in  dis- 
tilling gasoline  may  be  a  gas  burner,  an  alcohol  lamp,  or  an  electric 
heater. 

PROCEDURE  AND  DETAILS  OF  MANIPULATION  IN  CONDUCTING 
DISTILLATIONS 

1.  If  an  electric  heater  is  used  it  is  started  first  to  warm  it. 

2.  The  condenser  box  is  filled  with  water  containing  a  liberal  portion 
of  cracked  ice. 

3.  The  charge  of  gasoline  is  measured  into  the  clean,  dry  Engler 
flask  from  a  100  c.c.  graduate.     The  graduate  is  used  as  a  receiver  for 
distillates  without  any  drying.     This  procedure  eliminates  errors  due 
to  incorrect  scaling  of  graduates  and  also  avoids  the  creation  of  an 


200  GAS  AND  FUEL  ANALYSIS 

apparent  distillation  loss  due  to  the  impossibility  of  draining  the  gasoline 
entirely  from  the  graduate. 

4.  The  above-mentioned  graduate  is  placed  under  the  lower  end  of 
the  condenser  tube  so  that  the  latter  extends  downward  below  the  top 
of  the  graduate  at  least  1  in.     The  condenser  tube  should  be  so  shaped 
and  bent  that  the  tip  can  touch  the  wall  of  the  graduate  on  the  side 
adjacent  to  the  condenser  box.     This  detail  permits  distillates  to  run 
down  the  side  of  the  graduate  and  avoids  disturbance  of  the  meniscus 
caused  by  the  falling  of  drops.     The  graduate  is  moved  occasionally  to 
permit  the  operator  to  ascertain  that  the  speed  of  distillation  is  right, 
as  indicated  by  the  rate  at  which  drops  fall.     The  proper  rate  is  from 
4  c.c.  to  5  c.c.  per  minute,  which  is  approximately  two  drops  a  second. 
The  top  of  the  graduate  is  covered,  preferably  by  several  thicknesses 
of  filter  paper,  the  condenser  tube  passing  through  a  snugly  fitting 
opening.     This  minimizes  evaporation  losses  due  to  circulation  of  air 
through  the  graduate  and  also  excludes  any  water  that  may  drip  down 
the  outside  of  the  condenser  tube  on  account  of  condensation  on  the 
ice-cooled  condenser  box. 

5.  A  boiling  stone  (a  bit  of  unglazed  porcelain  or  other  porous  mate- 
rial) is  dropped  into  the  gasoline  in  the  Engler  flask.     The  thermometer 
is  equipped  with  a  well-fitted  cork  and  its  bulb  covered  with  a  thin  film 
of  absorbent  cotton  (preferably  the  long-fibered  variety  sold  for  surgical 
dressing).     The  quantity  of  cotton  used  shall  be  not  less  than  0.005 
nor  more  than  0.010  g.  (5  to  10  milligrams).     The  thermometer  is  fitted 
into  the  flask  with  the  bulb  just  below  the  lower  level  of  the  side  neck 
opening.     The  flask  is  connected  with  the  condenser  tube. 

6.  Heat  must  be  so  applied  that  the  first  drop  of  the  gasoline  falls 
from  the  end  of  the  condenser  tube  in  not  less  than  five  or  more  than 
ten  minutes.     The  initial  boiling  point  is  the  temperature  shown  by 
the  thermometer  when  the  first  drop  falls  from  the  end  of  the  condenser 
tube  into  the  graduate.     The  operator  should  not  allow  himself  to  be 
deceived  as  sometimes  (if  the  condenser  tube  is  not  dried  from  a  previous 
run)  a  drop  will  be  obtained  and  it  will  be  sometime  before  a  second  one 
falls;  in  this  case  the  first  drop  should  be  ignored.     The  amount  of 
heat  is  then  increased  so  that  the  distillation  proceeds  at  a  rate  of  from 
4  c.c.  to  5  c.c.  per  minute.     The  thermometer  is  read  as  each  of  the 
selected  percentage  marks  is  reached.     The  maximum  boiling  point  or 
dry  point  is  determined  by  continuing  the  heating  after  the  flask  bottom 
has  boiled  dry  until  the  column  of  mercury  reaches  a  maximum  and 
then  starts  to  recede  consistently. 

7.  Distillation  loss  is  determined  as  follows:  The  condenser  tube  is 
allowed  to  drain  for  at  least  five  minutes  after  heat  is  shut  off,  and  a 


LIQUID  FUELS  201 

final  reading  taken  of  the  quantity  of  distillate  collected  in  the  receiving 
graduate.  The  distillation  flask  is  removed  from  the  condenser  and 
thoroughly  cooled  as  soon  as  it  can  be  handled.  The  condensed  residue 
is  poured  into  a  small  graduate  or  graduated  test  tube  and  its  volume 
measured.  The  sum  of  its  volume  and  the  volume  collected  in  the 
receiving  graduate,  subtracted  from  100  c.c.  gives  the  figure  for  dis- 
tillation loss. 

11.  Kerosene. — Kerosene  is  usually  ranked  as  an  illuminating 
oil  rather  than  as  a  fuel  oil  and  tests  are  framed  to  determine  its 
suitability  for  use  in  lamps.  The  most  important  test  for  this 
purpose  is  the  flash  test  which  insures  safety  from  explosion 
caused  by  accumulation  of  combustible  vapors  in  the  bowl  of 
the  lamp.  Various  specifications  have  been  written  for  kerosene 
but  the  recommendations  of  the  Committee  on  Standardization 
of  Petroleum  Specifications1  will  probably  supplant  the  others. 
The  tests  and  specifications  for  water-white  kerosene  are  quoted 
below.  Tests  and  specifications  for  long-time  burning  oil,  300 
degree  mineral  seal  oil  and  signal  oil  are  also  included  in  the 
same  bulletin. 

WATER- WHITE  KEROSENE.     METHODS  OF  TEST 

Flash. — To  be  taken  on  the  Tag  closed  cup,  A.  S.  T.  M.  standard; 
oil  to  be  heated  at  the  rate  of  2°  F.  per  minute;  test  flame  to  be  applied 
every  2°,  commencing  at  105°  F. 

Color. — To  be  determined  on  the  Saybolt  colorimeter  or  its  equivalent. 

Sulphur. — Test  to  be  made  by  burning  at  least  2  grams  of  the  oil 
in  a  small  flask  and  absorbing  the  gases  of  combustion  in  a  standard 
solution  of  Sodium  Carbonate  and  titrating  the  excess  of  Sodium  Car- 
bonate with  the  standard  solution  of  Sulphuric  Acid. 

Floe. — Directions  for  making  test:  Take  a  hemispherical  iron  dish, 
and  place  a  small  layer  of  sand  in  the  bottom.  Take  a  500  c.c.  Florence 
or  Erlenmeyer  flask  and  into  it  put  300  c.c.  of  the  oil  (after  filtering 
if  it  contains  suspended  matter).  Suspend  a  thermometer  in  the  oil 
by  means  of  a  cork  slotted  on  the  side.  Place  flask  containing  the  oil 
in  the  sand  bath,  and  heat  bath  so  that  the  oil  has  reached  a  tempera- 
ture of  240°  F.  at  the  end  of  one  hour.  Hold  oil  at  temperature  of  not 
less  than  240°  F.  nor  more  than  250°  F.  for  six  hours.  The  oil  may 
become  discolored  but  there  should  be  no  suspended  matter  formed  in 

1  Bulletin  No.  2,  U.  S.  Fuel  Administration,   1918. 


202  GAS  AND  FUEL  ANALYSIS 

the  oil.  The  flask  should  be  given  a  slight  rotary  motion  and  if  there 
is  a  trace  of  "floe"  it  can  be  seen  to  rise  from  the  Center  of  the  bottom. 

Distillation  Test. — The  oil  shall  all  distill  below  temperature  of  600°  F. 
The  test  is  made  as  described  by  the  Bureau  of  Mines,  Technical  Papers 
166,  using  A.  S.  T.  M.  apparatus  with  wet  bulb  and  total  immersion 
thermometer. 

Cloud  Test. — Directions  for  making  test:  Take  a  4-ounce  oil  sample 
bottle  and  introduce  therein  1)^  ounces  of  the  oil  to  be  tested;  insert 
cork  with  cold-test  thermometer  so  that  thermometer  is  suspended  in 
the  oil.  Place  bottle  in  a  freezing  mixture  and  cool  to  0°  F.  Keep 
oil  cooled  to  this  temperature  for  10  minutes.  Bottle  should  be  given 
a  rotary  motion  occasionally  so  as  not  to  supercool  the  sides.  The  oil 
should  not  be  clouded  from  crystals  of  paraffin  wax  at  the  end  of  10 
minutes. 

Reaction. — Two  ounces  of  the  oil  should  be  shaken  with  one-half 
ounce  of  warm  neutral  distilled  water  and  allowed  to  cool  and  separate. 
The  water  when  separated  shall  react  neutral  to  methyl-orange  and 
phenol-phthalein. 

Burning  Test. — The  oil  must  burn  freely  and  steadily  in  a  lamp  fitted 
with  a  No.  1  sun  hinge  burner.  It  must  give  a  good  flame  for  a  period 
of  18  hours  without  smoking  or  forming  "ears"  or  "toad-stools"  on 
the  wick.  The  chimney  must  be  only  slightly  clouded  or  stained  at 
the  end  of  the  test. 

SUMMARY  OF  SPECIFICATIONS — WATER-WHITE  KEROSENE 

Appearance. — Oil  must  be  free  from  water,  glue,  and  suspended 
matter. 

Flash. — Not  less  than  115°  F.,  Tag  closed  cup,  A.  S.  T.  M.  standard. 

Color. — To  be  21  color  on  Saybolt  colorimeter  or  its  equivalent  on 
a  Lovibond  tintometer,  these  being  equal  to  color  of  a  solution  of 
Potassium  Bichromate  containing  0.0048  grams  per  liter. 

Sulphur. — Not  more  than  0.06  per  cent. 

Floe. — Oil  to  be  free  from  floe. 

Distillation. — Oil  to  distill  below  temperature  of  600°  F. 

Cloud  Test. — Oil  should  not  show  cloud  at  0°  F. 

Reaction. — Must  be  neither  acid  nor  alkaline. 

Burning  Test. — As  stated  above. 

12.  Fuel  Oil. — Tentative  regulations  for  the  storage  and  use 
of  the  fuel  oil  were  adopted  by  the  Committee  on  Inflammable 
Liquids  of  the  National  Fire  Protection  Association  in  1919.1 

1  Chemical  and  Metallurgical  Engineering  21,  781  (1919). 


LIQUID  FUELS  203 

This  committee  defined  oil-burning  equipments  as  those  using 
only  liquids  having  a  flash  point  above  150°  F.  in  a  closed  cup 
tester.  Specifications  for  fuel  oil  have  not  been  standardized. 
In  addition  to  flash  point  a  distillation  test  is  sometimes  speci- 
fied, since  a  mixed  product  of  a  heavy  residuum  and  a  light  naph- 
tha does  not  behave  so  well  in  the  burners  as  a  straight  product. 
The  oil  should  be  free  from  water  and  excessive  amounts  of  sul- 
phur. The  latter  may  be  determined  by  fusion  with  sodium 
peroxide  according  to  the  method  given  for  coal  in  Chapter  XV. 


CHAPTER  XIV 
SAMPLING  COAL 

1.  General  Consideration. — However  accurate  an  analysis 
of  coal  may  be,  the  results  are  of  little  value  and  are  often  worse 
than  useless  if  the  sample  submitted  to  the  analyst  is  not  a  repre- 
sentative one.  Elaborate  methods  have  been  worked  out  for 
sampling  gold  and  silver  ores  but  cost  precludes  the  application 
of  anything  but  the  simplest  methods  to  coal.  It  is  manifest 
that  it  is  unwise  to  spend  ten  cents  a  ton  to  determine  whether 
the  price  is  two  cents  a  ton  too  high.  If  we  assume  a  shipment  of 
a  single  car  of  coal  weighing  forty  tons,  which  must  be  sampled 
and  analyzed  by  itself,  it  will  be  seen  that  a  charge  of  eight 
dollars  for  this  service  will  add  twenty  cents  per  ton  to  the  price 
of  coaL  This  is  nearly  10  per  cent,  of  the  cost  of  the  coal  at 
the  mouth  of  the  mine  and  is  an  expense  which  is  hardly  justifiable. 

However  if  the  test  is  worth  making  at  all  it  must  be  on  a 
sample  which  has  fair  claim  to  representativeness.  The  coal 
sampler  stands  eternally  between  the  devil  of  inadequateness 
and  the  deep  sea  of  excessive  cost.  In  large  plants  where 
the  coal  is  immediately  crushed  and  removed  to  storage  bins  by 
conveyors  a  representative  sample  may  readily  be  obtained.  In 
most  cases,  however,  the  coal  must  be  sampled  as  it  comes  from 
the  car  and  the  problem  is  more  difficult. 

To  many  people  coal  is  black  and  all  that  is  black  is  coal. 
The  more  careful  observer  may  detect  bits  of  slate,  and  streaks 
or  nodules  of  the  brassy  looking  pyrites.  The  chemist  knows 
that  in  addition  the  fine  particles  which  have  crushed  because  of 
their  greater  friability  differ  in  composition  from  the  lump  coal 
and  are  usually  higher  in  ash,  though  sometimes  the  reverse  is 
the  case,  and  that  coal  is  far  from  being  a  mass  of  uniform 
composition. 

204 


SAMPLING  COAL  205 

2.  Difference  in  Composition  of  Lump  and  Fine  Coal. — The 

following  tests  taken  from  the  author's  record  of  cooperative 
tests  undertaken  jointly  by  the  University  of  Michigan  Gas  Ex- 
periment Station  and  the  United  States  Bureau  of  Mines  to 
determine  the  availability  of  various  coals  for  gas  manufacture 
show  some  interesting  variations.  The  coals  had  mostly  been 
shipped  in  small  lots  in  sacks  and  were  therefore  considerably 
cru&hed  in  transit.  They  were  screened  in  lots  of  about  600  Ib. 
on  a  three-quarter  inch  bar  screen  preparatory  to  gas  tests  and 
the  screenings  and  lump  coal  were  separately  sampled. 

The  sampling  of  the  fine  coal  presented  no  difficulty  since  it 
was  already  in  small  lumps  and  could  be  crushed  as  fine  as  de- 
sired. The  lump  coal  could  not  be  finely  crushed  without 
detriment  to  the  gas  tests  and  so  it  was  sampled  by  breaking 
the  large  lumps  and  then  taking  about  two  scoopf uls  which  were 
crushed  and  sampled  as  usual.  Of  the  eleven  coals  tested  in 
this  manner  four,  one  each  from  West  Virginia,  Colorado,  New 
Mexico  and  Wyoming  showed  very  little  difference  between  the 
lumps  and  screenings.  One  coal  showed  decidedly  less  ash  in 
the  screenings  than  in  the  lump  coal.  Six  coals  showed  notice- 
able and  in  some  cases  notable  increases  of  ash  and  sulphur  in 
screenings  with  corresponding  decreases  of  heating  value,  as 
shown  by  the  following  analyses  of  the  coals  calculated  to  a  dry 
basis. 

In  the  coal  from  Hellier,  Kentucky  for  which  there  are  three 
tests,  the  average  heating  value  of  the  screenings  is  1080  B.t.u. 
lower  than  that  of  the  lump.  This  is  entirely  due  to  difference  in 
ash  as  shown  by  the  figures  for  heating  value  figured  to  coal  dry 
and  free  from  ash,  where  the  difference  disappears,  the  average 
heating  value  of  the  screenings  being  only  6  B.t.u.  below  that  of 
the  lump.  The  same  thing  is  true  of  the  other  coals  of  the  list — 
the  variation  in  heating  value  of  lump  and  screenings  disappears  al- 
most completely  when  calculated  to  a  moisture  and  ash-free  basis. 

Sulphur  is  never  lower  in  the  screenings  than  in  the  lump  and 
is  in  some  cases  nearly  twice  as  high. 

The  last  coal  in  the  above  table  differs  from  all  the  others  in 
that  the  screenings  are  much  lower  in  ash  than  the  lump.  It 
might  be  thought  that  the  sample  had  been  labelled  incorrectly 


206 


GAS  AND  FUEL  ANALYSIS 


£12 


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a  .s 
S  8 

PH    S 


rH    O    O    O    O    i-     rH    C<l    CO    T- 


Tj<<N<NO5OiTtHCOO500Oi 
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C5T-HOT^COr^i-(iOI> 
COC<ICOiOCOCOCOCO      1 


SAMPLING  COAL  207 

of  it  were  not  for  the  check  afforded  by  analysis  of  the  coke  made 
from  the  lump  coal.  The  coke  contained  25.3  per  cent,  of  ash, 
a  figure  which  agrees  well  with  the  calculated  result  of  24.3  per 
cent.  It  is  evident  that  in  this  coal  the  coal  substance  is  the 
friable  constituent  while  the  ash  forms  a  cementing  material. 
The  heating  value  of  the  dry  screenings  is  1366  B.t.u.  higher 
than  the  lump,  but  when  the  ash  is  eliminated  by  calculation, 
the  difference  drops  to  61  B.t.u. 

These  figures  show  that  the  heating  value  of  lump  coal  may 
vary  as  much  as  2000  B.t.u.  from  that  of  fine  coal  and  that 
usually  the  fine  coal  will  contain  more  ash  and  have  the  lower 
heat  value.  Occasionally  the  reverse  is  the  case.  The  true 
coal  as  reckoned  to  a  moisture  and  ash  free  basis  has  practically 
the  same  heating  value  irrespective  of  its  physical  fineness. 

3.  A  Scoopful  as  a  Sample. — It  is  commonly  held  that  a 
few  scoopfuls  should  be  representative  of  a  carload.  This 
question  was  put  to  a  practical  test  by  Bailey1  who  had  a  lot 
of  3  tons  of  run-of-mine  coal  carted  away  in  wheel  barrows. 
As  each  barrow  was  filled  a  shovelful  of  coal  was  put  into, 
not  one,  but  into  each  of  sixteen  sample  barrels.  After  the 
pile  had  disappeared  there  were  left  the  sixteen  sample  barrels 
each  with  about  125  Ib.  of  coal.  These  samples  were  crushed 
and  sampled  carefully  and  the  ash  in  each  was  determined. 
The  results  were  as  follows: 

Per  cent,  ash 

1 9.68 

2 10.28 

3 13 . 92  Maximum 

4 11.22 

5 10.88 

6 9.80 

7 11.84 

8 10.28 

9 10.10 

10 10.64 

11 10.06 

12 10.72 

13 9.46  Minimum 

14 9.66 

15 11.08 

16 11.34 

1  Trans.  Am.  Soc.  Mech.  Eng.,  27,  639  (1906). 


208 


GAS  AND  FUEL  ANALYSIS 


These  samples  which  should  have  given  results  in  close  agree- 
ment show  an  extreme  variation  of  4.46  per  cent,  in  their  ash 
content.  Had  the  heating  values  of  these  samples  been  deter- 
mined they  .would  of  course  have  shown  similar  discrepancies. 
If  this  coal  had  been  sold  on  a  premium  and  penalty  basis  and 
the  coal  with  the  average  ash  content  of  10.68  had  been  accepted 
without  premium  or  penalty,  the  penalty  on  a  basis  of  sample 
No.  3  might  readily  have  been  twelve  or  fifteen  cents  per  ton. 
And  yet  in  this  test  the  sample  consisted  of  four  or  five  shovel- 
fuls taken  from  a  lot  as  small  as  3  tons  and  not  from  a  whole  car 
load. 

4.  Influence  of  Lumps  of  Slate. — It  is  manifest  that  if  all 
the  ash  of  coal  were  to  be  concentrated  in  lumps  the  size  of  a 
football,  that  a  single  scoopful  of  coal  would  either  show  no 
ash  or  else  an  exorbitantly  high  amount.  The  error  would 
be  much  less  if  the  ash  were  in  lumps  only  the  size  of  walnuts 
and  still  less  if  it  were  more  finely  divided.  Even  if  the  ash 
were  in  large  pieces  if  a  sufficient  number  of  scoops  should  be 
taken  for  analysis  an  average  of  all  the  figures  would  give  a 
correct  result.  Bailey1  gives  the  following  table  derived  partly 
experimentally  and  partly  mathematically  showing  the  relation 
between  the  size  of  the  largest  piece  of  slate  and  the  weight  of 
the  sample  which  must  be  taken  in  order  that  error  in  sampling 
shall  not  cause  an  error  of  over  1  per  cent,  in  the  ash. 


Size  of  slate, 
inches 

Wt.  largest  piece  of 
slate,  pounds 

Original  sample  should 
weigh,  pounds 

4 
3 
2 
1 
0.75 
0.50 

6.7 
2.5 
0.75 
0.12 
0.046 
0.018 

39,000 
12,500 
3,800 
600 
230 
90 

Since  there  are  very  few  shipments  of  coal  other  than  the 
small  sizes  of  anthracite  which  may  not  contain  pieces  of  slate 
weighing  a  pound  it  is  evident  that  on  this  basis  a  sample  of 
less  than  2  tons  cannot  be  considered  representative.  Any 
smaller  sample  whether  it  be  drawn  from  a  wagon  load  or  a 

1  Jour.  Ind.  and  Eng.  Chem.,  1,  176  (1909). 


SAMPLING  COAL  209 

train  of  cars  cannot  be  considered  as  representative  of  anything 
except  itself. 

6.  Taking  a  Sample. — It  is  fatal  for  a  sampler  to  try  to 
pick  an  average  sample  by  taking  what  seems  to  him  a  fair 
proportion  of  coarse  and  fine,  and  rejecting  material  that  looks 
either  exceptionally  good  or  bad.  The  only  way  is  to  determine 
how  a  most  representative  sample  may  be  secured  in  a  reasonable 
manner  and  then  to  carry  out  the  operation  as  mechanically 
as  possible. 

If  the  sample  is  being  taken  from  a  wagon  the  shovel  should 
be  run  along  the  bottom  of  the  wagon  after  enough  has  been 
unloaded  to  allow  the  coal  to  assume  its  natural  slope.  The 
same  procedure  may  be  followed  when  coal  is  being  shovelled 
from  flat-bottomed  cars.  Where  cars  or  wagons  are  being 
dumped  the  scoop  may  be  held  in  the  stream  of  falling  coal. 
If  cars  are  to  be  sampled  before  unloading,  a  trench,  or  better 
two  trenches,  each  12  in.  deep  should  be  dug  across  the  car  in 
order  to  remove  excess  of  dust  and  cinder  as  well  as  snow  which 
may  have  collected  in  the  top  layers.  The  sample  is  to  be 
taken  from  the  bottom  of  the  trench.  It  is  evident  that  coal 
sampled  in  this  way  will  contain  too  small  a  proportion  of  fine 
coal,  most  of  which  will  have  sifted  to  the  floor  of  the  car.  It 
is  therefore  preferable  to  sample  during  unloading. 

If  it  is  necessary  to  determine  the  moisture  in  a  car  of  coal 
which  arrives  wet  or  covered  with  ice  the  problem  of  sampling 
becomes  even  more  complex.  Fortunately,  specifications  are 
usually  based  on  dry  or  air-dry  coal  so  that  the  accidental 
moisture  acquired  in  transit  is  not  usually  of  importance. 

6.  Mine  Sampling. — The  methods  of  sampling  coal  in  a  mine 
as  recommended  by  the  U.  S.  Bureau  of  Mines  have  been  fully 
described  by  Holmes.1  He  recommends  that  for  mines  shipping 
200  tons  or  less  daily,  at  least  four  samples  should  be  taken. 
In  general  only  clean,  fresh  coal  should  be  taken  and  weathered 
coal  should  be  avoided.  Before  cutting  a  sample  the  face  of  the 
bed  and  the  roof  is  to  be  cleaned  of  loose  fragments  which 
might  drop  into  the  sample  and  a  band  1  ft.  wide  extending 
from  floor  to  roof  is  to  be  cut  back  at  least  an  inch  to  expose 
fresh  coal.  The  sample  as  cut  from  this  prepared  face  should 

1  Technical  Paper  1,  Bureau  of  Mines,  1911. 


210  GAS  AND  FUEL  ANALYSIS 

include  everything  which  the  miner  includes  in  the  coal  pre- 
pared for  the  market  and  should  exclude  the  thick  partings  and 
large  lenses  of  pyrite  which  are  thrown  out  by  the  miner.  The 
cut  should  be  made  perpendicularly  about  2  in.  deep  and  6  in. 
wide  so  that  there  will  be  about  6  Ib.  of  coal  chips  for  each  foot 
of  thickness  of  the  vein.  These  chips  are  to  be  caught  on  the 
waterproof  sample  blanket  and  crushed  to  pass  a  ^-in.  screen. 
The  sample  is  then  quartered  down  and  placed  in  a  tight  sample 
can  All  the  operations  are  to'  be  carried  on  in  the  mine  so  as 
not  to  expose  the  coal  to  the  outside  atmosphere. 

7.  Preparation  of  Sample. — The  initial  sample  must  be  crushed 
and  subdivided  until  it  is  finally  ready  for  the  chemical  analysis. 
Care  must  be  taken  that  it  does  not  change  during  this  process. 
It  is  almost  impossible  to  prevent  the  moisture  from  changing 
and  where  it  is  necessary  to  determine  this,  the  whole  sample  is 
usually  weighed  and  allowed  to  dry  in  a  warm  room  until  it 
has  become  approximately  air-dry,  when  it  is  again  weighed. 
It  is  in  any  case  difficult  to  sample  coal  which  is  very  wet  or 
covered  with  ice  and  a  preliminary  air-drying  is,  where  possible, 
always  advisable.  The  sample  must  now  be  crushed  and  sub- 
divided. Where  a  well-equipped  sampling  laboratory  is  avail- 
able the  crushing  will  of  course  be  easily  accomplished  by 
crushers  and  the  subdivisions  either  made  by  mechanical  sam- 
plers or  upon  clean  iron  plates.  In  such  cases  there  is  very  little 
liability  to  error  in  this  stage  of  the  process.  In  many  cases, 
however,  the  crushing  and  subdivisions  must  be  carried  out  by 
hand,  often  on  the  floor  of  the  boiler  room  and  frequently  under 
even  less  favorable  conditions.  The  first  requisite  is  cleanliness 
of  the  sampling  surface.  It  is  always  preferable  to  sample  on  a 
metal  plate.  A  cement  floor  is  to  be  looked  upon  with  suspicion 
and  not  to  be  used  unless  it  is  hard  and  fails  to  yield  appreciable 
sand  on  vigorous  sweeping.  The  liability  to  error  is  not  great 
while  the  sample  is  large.  When  it  becomes  small  enough  it 
should  be  placed  on  oil  cloth  if  a  metal  plate  is  not  available. 
The  details  of  this  process  are  given  in  section  10  of  this  chapter. 

8.  Preservation  of  Sample. — If  the  percentage  of  moisture  in 
the  coal  is  of  importance  the  sample  should  be  placed  in  an  air- 
tight receptacle  and  kept  in  a  cool  place.  Coal  which  is  not 
finely  powdered  does  not  change  rapidly  but  it  is  advisable  to 


SAMPLING  COAL 


211 


have  the  analysis  made  promptly.  Porter  and  Ovitz1  have 
shown  that  samples  of  coal  evolve  methane  and  carbon  dioxide 
and  absorb  oxygen  for  a  period  of  several  months.  The  changes 
due  to  the  evolution  of  methane  seldom  rise  above  one-tenth  of 
1  per  cent.  The  changes  due  to  addition  of  oxygen  are  less 
certain  but  would  seem  to  be  possibly  as  high  as  0.5  per  cent. 
Parr  has  shown  that  Illinois  coals  may  lose  in  heat  value  from 
0.5  to  1  per  cent,  in  the  first  ten  days  after  mining  and  during 
the  process  of  preparing  the  sample  for  analysis.  The  rapid 
changes  take  place  soon  after  the  coal  is  mined  and  the  rate  of 
change  has  usually  materially  decreased  before  the  coal  is  sampled 
by  the  consumer. 

9.  Usual  Accuracy  of  Sampling. — The  figures  given  by  Bailey 
show  that  an  accuracy  of  1  per  cent,  in  the  ash  is  not  to  be  ex- 
pected by  ordinary  methods.  The  following  tables  give  some 
data  resulting  from  the  sampling  of  two  separate  carloads  of 
coal.  Four  separate  samples  were  taken  from  each  car  after 
loading  at  the  mine  by  an  inspector  of  the  Bureau  of  Mines.  The 
same  cars  were  sampled  especially  carefully  after  arrival  at  their 
destination,  one-sixth  of  each  carload  being  systematically  sepa- 
rated as  it  was  unloaded  for  the  initial  sample.  This  initial 
sample  was  cut  into  four  separate  ones  which  were  separately 
sampled  and  analyzed.  There  are  eight  different  samples  from 
each  carload  whose  analyses  are  tabulated  in  the  accompanying 
table. 

PITTSBURG  COAL,  A.  A.  15 


Air-dried  coal 

B.t.u.  of  coal 
free  from  mois- 
ture and  ash 

Moisture 

Ash 

S 

B.t.u. 

Car  at  mine 

No.  1... 

0.95 

6.27 

0.91 

14213 

15319 

No.  2... 

1.00 

5.55 

0.72 

14315 

15318 

No.  3... 

0.98 

6.23 

0.98 

14182 

15284 

No.  4... 

0.96 

6.91 

0.84 

14107 

15295 

Average 

0.97 

6.24 

0.86 

14204 

15304 

Car   as   un- 

No. 1... 

1.11 

5.99 

0.82 

14215 

15301 

loaded 

No.  2... 

0.97 

6.54 

0.93 

14137 

15284 

No.  3... 

1.01 

5.63 

0.80 

14285 

15300 

No.  4... 

1.08 

5.88 

0.81 

14206 

15269 

Average 

1.04 

6.00 

0.84 

14211 

15288 

Technical  Paper  2,  Bureau  of  Mines,  1911. 


212 


GAS  AND  FUEL  ANALYSIS 


FAIRMONT  COAL,  A.  A.  16 


Air-dried  coal 

B.t.u.  of  coal 
free  from  mois- 
.  ture  and  ash 

Moisture  |    Ash 

S      |  B.t.u. 

Car  at  mine. 

No.  1... 

1.10 

7.62 

0.67 

13925 

15255 

No.  2... 

1.10 

7.71 

0.64 

13874 

15216 

No.  3... 

1.07 

9.23 

0.83 

13678 

15240 

No.  4... 

1.17 

6.20 

0.52 

14096 

15217 

Average 

1.11 

7.69 

0.66 

13898 

15232 

Car   as   un- 

No. 1... 

1.24 

8.87 

0.64 

13671 

15209 

loaded 

No.  2... 

1.21 

8.98 

0.69 

13640 

15188 

No.  3... 

1.28 

8.89 

0.69 

13638 

15182 

No.  4... 

1.27 

9.06 

0.73 

13604 

15160 

Average 

1.24 

8.95 

0.69 

13638 

15185 

The  chief  variable  in  these  samples  is  the  ash  which  in  turn 
affects  the  heating  value.  The  accuracy  of  the  analyses  is  at- 
tested by  the  close  agreement  of  the  heating  value  referred  to  coal 
dry  and  free  from  ash.  In  the  Fairmont  coal  the  heating  value 
of  the  coal  taken  at  the  mine  is  noticeably  higher  than  that  sam- 
pled from  the  car,  when  calculated  to  an  ash  and  moisture  free 
basis,  due  possibly  to  escape  of  gas  from  the  freshly  mined  coal. 

The  average  ash  content  of  the  Pittsburgh  coal  is  closely  the 
same  in  the  two  sets  but  in  the  Fairmont  coal  the  average  ash 
as  sampled  from  the  car  at  the  mine  was  1.6  per  cent,  lower  than 
that  obtained  as  the  car  was  unloaded.  As  was  pointed  out 
above,  this  variation  is  a  normal  one  due  to  the  method  of  sam- 
pling. The  variation  in  the  average  heating  value  of  these  two 
series  amounts  to  260  B.t.u.,  a  figure  which  might  easily  cause  a 
difference  in  price  of  eight  cents  a  ton. 

Turning  from  averages  to  individual  figures  we  find  a  better 
agreement  with  the  Pittsburgh  than  the  Fairmont  coal,  and  in 
each  series  the  agreement  better  between  the  samples  taken  from 
the  car  as  unloaded,  as  should  have  been  the  case.  The  extremes 
for  the  Fairmont  coal  are  tabulated  as  follows: 


Low  ash 

High  ash 

Difference 

per  cent,  ash 

B.t.u. 

per  cent,  ash 

B.t.u. 

per  cent,  ash 

B.t.u. 

Car  at  mine  
Car  as  unloaded  . 

6.20      . 
8.87 

14096 
13671 

9.23 
9.06 

13678 
13604 

3.03 
0.19 

418 
69 

SAMPLING  COAL  213 

The  agreement  between  the  samples  taken  very  carefully 
from  the  car  as  unloaded  is  excellent.  Tne  difference  between 
the  extremes  of  the  samples  taken  from  the  loaded  car  which 
amounts  to  418  B.t.u.  might  readily  cause  a  difference  of  fifteen 
cents  a  ton  on  the  settlement  price  of  the  coal. 

The  engineers  of  the  U.  S.  Bureau  of  Mines1  have  studied 
the  error  in  sampling  ten  different  lots  of  coal.  Each  of  two  in- 
spectors collected  a  sample  of  100  Ib.  from  a  given  lot  of  coal. 
In  lot  a  their  samples  differed  in  heating  value  by  158  B.t.u.  per 
pound  of  dry  coal.  They  then  each  collected  a  second  sample 
of  100  Ib.  and  averaged  the  results  of  this  with  their  first  sample. 
The  difference  between  the  two  collectors  then  dropped  to  132 
B.t.u.  In  the  same  way  they  continued  to  take  successive  sam- 
ples of  100  Ib.  and  average  all  of  their  results  and  after  ten  of 
such  samples  had  been  taken  the  differences  between  the  averages 
for  each  man  was  small.  As  the  result  of  tests  on  ten  different 
lots  of  coal  they  found  that  it  was  necessary  to  collect  and  average 
seven  different  samples  of  100  Ib.  each  in  order  that  the  result 
obtained  by  two  collectors  should  not  differ  by  more  than  50 
B.t.u.  Their  average  results  are  given  in  the  following  table: 

AVERAGE  ERROR  IN  SAMPLING  10  LOTS  OF  COAL  AS  SHOWN 
BY  THE  DISAGREEMENT  IN  HEATING  VALUE  OF  SUC- 
CESSIVE SAMPLES  TAKEN  BY  TWO  COLLECTORS 


Disagreement  between  two 

collectors  in  B.t.u.  per 

pound  dry  coal 


First  sample  of  100  Ib 

Average  of  2  samples  of  100  Ib 

Average  of  3  samples  of  100  Ib 

Average  of  4  samples  of  100  Ib 

Average  of  5  samples  of  100  Ib 

Average  of  6  samples  of  100  Ib 

Average  of  7  samples  of  100  Ib 

Average  of  8  samples  of  100  Ib 

Average  of  9  samples  of  100  Ib 

Average  of  10  samples  of  100  Ib 

Average  of  11  samples  of  100  Ib 

Average  of  12  samples  of  100  Ib 

Average  of  13  samples  of  100  Ib 


251 

200 

125 

111 

75 

78 

51 

53 

44 

37 

32 

32 

25 


1  Bui  63,  Bureau  of  Mines, 


214  GAS  AND  FUEL  ANALYSIS 

10.  Standard  Methods  of  Sampling. — Directions  for  sampling 
and  also  specifications  for  coal  as  purchased  by  the  United  States 
Government  are  given  in  publications  of  the  Bureau  of  Mines.1 
The  American  Society  for  Testing  Materials  adopted  in  19162  a 
standard  method  for  sampling  coal  which  is  quoted  below: 

FOR  ALL  DETERMINATIONS  EXCEPT  TOTAL  MOISTURE 

1.  The  coal  shall  be  sampled  when  it  is  being  loaded  into  or  unloaded 
from  railroad  cars,  ships,  barges,  or  wagons,  or  when  discharged  from 
supply  bins,  or  from  industrial  railway  cars,  or  grab  buckets,  or  from 
any  coal-conveying  equipments,  as  the  case  may  be.     If  the  coal  is 
crushed  as  received,  samples  usually  can  be  taken  advantageously  after 
the  coal  has  passed  through  the  crusher.     Samples  collected  from  the 
surface  of  coal  in  piles  or  bins,  or  in-  cars,  ships  or  barges  are  generally 
unreliable. 

2.  To  collect  samples,  a  shovel  or  specially  designed  tool,  or  mechan- 
ical means  shall  be  used  for  taking  equal  portions  or  increments.     For 
slack  or  small  sizes  of  anthracite,  increments  as  small  as  5  to  10  Ib. 
may  be  taken  but  for  run-of-mine  or  lump  coal,  increments  should  be 
at  least  10  to  30  Ib. 

3.  The  increments  shall  be  regularly  and  systematically  collected,  so 
that  the  entire  quantity  of  coal  sampled  will  be  represented  proportion- 
ately in  the  gross  sample,  and  with  such  frequency  that  a  gross  sample 
of  the  required  amount  shall  be  collected.     The  standard  gross  sample 
shall  not  be  less  than  1000  Ib.  except  that  for  slack  coal  and  small  sizes 
of  anthracite  in  which  the  impurities  do  not  exist  in  abnormal  quantities 
or  in  pieces  larger  than  M  in.,  a  gross  sample  of  approximately  500  Ib. 
shall  be  considered  sufficient.     If  the  coal  contains  an  unusual  amount 
of  impurities,  such  as  slate,  and  if  the  pieces  of  such  impurities  are 
very  large,  a  gross  sample  of  approximately  1500  Ib.  or  more  should  be 
collected.     The  gross  sample  should  contain  the  same  proportion  of 
lump  coal,  fine  coal,  and  impurities  as  is  contained  in  the  coal  sampled. 
When  coal  is  extremely  lumpy,  it  is  best  to  break  a  proportional  amount 
of  the  lumps  before  taking  the  various  increments  of  a  sample.     Pro- 
vision should   be  made  for  the  preservation  of  the  integrity  of  the 
sample. 

4.  A  gross  sample  shall  be  taken  for  each  500  tons  or  less,  or  in  case 
of  larger  tonnages,  for  such  quantities  as  may  be  agreed  upon. 


1  Bulletin  116  and  Technical  Paper  133  by  Geo.  S.  Pope. 

2  A.  S.  T,  M,  Standards  issued  by  American  Society  for  Testing  Materials, 


SAMPLING  COAL  215 

TABLE  I 


Weight  of  sample 
to  be  divided,  Ib. 

Largest  size  of  coal  and  impurities 
allowable  in  sample  before 
division,  inches 

1000  or  over 
500 
250 
125 
60 
30 

1 

H 

M 
% 
H 

%Q  or  4-mesh  screen 

5.  After  the  gross  sample  has  been  collected,  it  shall  be  systematically 
crushed,  mixed,  and  reduced  in  quantity  to  convenient  size  for  trans- 
mittal  to  the  laboratory.     The  sample  may  be  crushed  by  hand  or  by 
any  mechanical  means,  but  under  such  conditions  as  shall  prevent  loss 
or  the  accidental  admixture  of  foreign  matter.     Samples  of  the  quan- 
tities indicated  in  Table  I  shall  be  crushed  so  that  no  pieces  of  coal  and 
impurities  will  be  greater  in  any  dimension,  as  judged  by  eye,  than 
specified  for  the  sample  before  division  into  two  approximately  equal 
parts. 

The  method  of  reducing  by  hand  the  quantity  of  coal  in  a  gross 
sample  shall  be  carried  out  as  prescribed  in  Section  6,  even  should  the 
initial  size  of  coal  and  impurities  be  less  than  indicated  in  Table  I. 

6.  The  progressive  reduction  in  the  weight  of  the  sample  to  the  quan- 
tities indicated  in  Table  1  shall  be  done  by  the  following  methods,  which 
are  illustrated  in  Fig.  47: 

(a)  The  alternate-shovel  method  of  reducing  the  gross  sample  shall 
be  repeated  until  the  sample  is  reduced  to  approximately  250  Ib.,  and 
care  shall  be  observed  before  each  reduction  in  quantity  that  the  sample 
has  been  crushed  to  the  fineness  prescribed  in  Table  I.  The  crushed 
coal  shall  be  shoveled  into  a  conical  pile  by  depositing  each  shovelful 
of  coal  on  top  of  the  preceding  one,  and  then  formed  into  a  long  pile  in 
the  following  manner:  The  sampler  shall  take  a  shovelful  of  coal  from 
the  conical  pile  and  spread  it  out  in  a  straight  line  having  a  width  equal 
to  the  width  of  the  shovel  and  a  length  of  5  to  10  ft.  His  next  shovelful 
shall  be  spread  directly  over  the  top  of  the  first  shovelful,  but  in  the 
opposite  direction,  and  so  on  back  and  forth,  the  pile  being  occasionally 
flattened,  until  all  the  coal  has  been  formed  into  one  lone  pile.  The 
sampler  shall  then  discard  half  of  this  pile,  proceeding  as  follows:  Be- 
ginning on  one  side  of  the  pile,  at  either  end,  and  shoveling  from  the 
bottom  of  the  pile,  the  sampler  shall  take  one  shovelful  and  set  it  aside; 
advancing  along  the  side  of  the  pile  a  distance  equal  to  the  width  of  the 
shovel,  he  shall  take  a  second  shovelful  and  discard  it ;  again  advancing 


216 


GAS  AND  FUEL  ANALYSIS 


F"st  stage  in  the 
preparation  of 
1.000. pound 

sample 


Crush  1,000-pound  sample  on 
hard,  clean  surface  to  I"  size 


1,000-pound  sample  crushed 
to  1"  and  coned 


Mix  by  forming  long  pile. 
A—  spreading  out  first  shovelful. 
B—  long  pile  completed 


Second  stage. 


Third  stage. 


Fourth  stage. 


Fifth  stage 


A-  spreading  out  first  shovelful. 
B—  long  pile  completed 


Crush  250-pound  sample  250-pounds  crushed  to  Jf  and  coned  Mix  by  forming  new  cone 


Crush  60-pound  sample  (fig.  22:  A,  A) 
to  !4"  size 


Mix  by  rolling  on  blanket 


Form  cone  after  mixing 


Sixth  stage. 


29 


Crush  30-pound  sample  (fig.  28:  A.  A)  Mix  by  rolling  on  blanket 

to%"  or  4-mesh  size 


31 


Form  cone  after  mixing 


FIG.  47. — Method  of  preparing  a  sample  of  coal  by  hand.  The  necessary 
rake.  The  coal  is  raked  while  being  crushed,  so  that  all  lumps  will  be 
sample  is  halved  or  quartered. 


SAMPLING  COAL 


217 


.'  alternate  shovel  method.  Long  pile  divided  into  two  parts; 

1 1, 3, 5,  etc.,  reserved  as  5,  A;  A—resene;  fl_  reject 

2, 4, 6.  etc..  rejected  as  5. B 


Shovelfuls^, 


alternate  shovel  method.  Long  pile  divided  into  two  parts; 

Ful» i, 3, 5,  etc.,  reserved  as I0i  A;  A- reserve;  B- reject 

2, 4,  6.  etc..  rejected  as  10,  B 


SELECT  A  HARD,  CLEAN 
SURFACE.  FREE  OF  CRACKS 
AND  PROTECTED  FROM 
RAIN,  SNOW,  WIND,  AND 
BEATING  SUN.  DO  NOT  LET 
CINDERS,  SAND,  CHIRPINGS 
FROM  FLOOR,  OR  ANY 
OTHER  FOREIGN  MATTER 
GET  INTO  THE  SAMPLE. 
PROTECT  SAMPLE  FROM 
LOSS  OR  GAIN  IN  MOISTURE 


Retain  opposite  quarters  A,  A 
Reject  quarters  B,  B 


Retain  opposite  quarters  A,  A 
Reject  quarters  B.  B 


Quarter  after  flattening  con* 


Sample  divided  into  quarter* 


Fill  two  5-pound  sample  containers  from 
A,  A,  One  for  laboratory,  one  for  reserve 


tools  are  a  shovel,  tamper,  blanket  measuring  about  6  by  8  feet,  broom,  and 
crushed.     Floor  or  blanket  is  swept  clean  of  discarded  coal  each  time  after 


218  GAS  AND  FUEL  ANALYSIS 

in  the  same  direction  one  shovel  width,  he  shall  take  a  third  shovelful 
and  add  it  to  the  first.  The  fourth  shall  be  taken  in  a  like  manner  and 
discarded,  the  fifth  retained,  and  so  on,  the  sampler  advancing  always 
in  the  same  direction  around  the  pile  so  that  its  size  will  be  gradually 
reduced  in  a  uniform  manner.  When  the  pile  is  removed,  about  half 
of  the  original  quantity  of  coal  should  be  contained  in  the  new  pile 
formed  by  the  alternate  shovelfulls  which  have  been  retained. 

(b)  After  the  gross  sample  has  been  reduced  by  the  above  method 
to  approximately  250  lb.,  further  reduction  in  quantity  shall  be  by  the 
quartering  method.     Before  each  quartering,  the  sample  shall  be  crushed 
to  the  fineness  prescribed  in  Table  I. 

Quantities  of  125  to  250  lb.  shall  be  thoroughly  mixed  by  coning  and 
re-coning;  quantities  less  than  125  lb.  shall  be  placed  on  a  suitable 
cloth,  measuring  about  6  by  8  ft.,  mixed  by  raising  first  one  end  of  the 
cloth  and  then  the  other,  so  as  to  roll  the  coal  back  and  forth,  and  after 
being  thoroughly  mixed  shall  be  formed  into  a  conical  pile  by  gathering 
together  the  four  corners  of  the  cloth.  The  quartering  of  the  conical 
pile  shall  be  done  as  follows: 

The  cone  shall  be  flattened,  its  apex  being  pressed  vertically  down 
with  a  shovel,  or  board,  so  that  after  the  pile  has  been  quartered,  each 
quarter  will  contain  the  material  originally  in  it.  The  flattened  mass, 
which  shall  be  of  uniform  thickness  and  diameter,  shall  then  be  marked 
into  quarters  by  two  lines  that  intersect  at  right  angles  directly  under 
a  point  corresponding  to  the  apex  of  the  original  cone.  The  diagonally 
opposite  quarters  shall  be  shoveled  away  and  discarded  and  the  space 
that  they  occupied  brushed  clean.  The  coal  remaining  shall  be  suc- 
cessively crushed,  mixed,  coned,  and  quartered  until  the  sample  is 
reduced  to  the  desired  quantity. 

(c)  The  30-lb.  quantity  shall  be  crushed  to  %g  in.  or  4-mesh  size, 
mixed,  coned,  flattened  and  quartered.     The  laboratory  samples  shall 
include  all  of  one  of  the  quarters,  or  all  of  two  opposite  quarters,  as  may 
be  required.     The  laboratory  sample  shall  be  immediately  placed  in  a 
suitable  container  and  sealed  in  such  a  manner  as  to  preclude  tampering. 

7.  Only  such  mechanical  means  as  will  give  equally  representative 
samples  shall  be  used  in  substitution  for  the  hand  method  of  preparation 
herein  standardized. 

II.  FOR  THE  DETERMINATION  OF  TOTAL  MOISTURE 

8.  The  special  moisture  sample  shall  weigh  approximately  100  lb., 
and  shall  be  accumulated  by  placing  in  a  waterproof  receptacle  with  a 
tight-fitting  and  waterproof  lid  small  equal  parts  of  freshly  taken  incre- 
ments of  the  standard  gross  sample.     The  accumulated  moisture  sample 


SAMPLING  COAL  219 

. 

shall  be  rapidly  crushed  and  reduced  mechanically  or  by  hand  to  about 
a  5-lb.  quantity,  which  shall  be  immediately  placed  in  a  container  and 
sealed  air-tight  and  forwarded  to  the  laboratory  without  delay. 

9.  Only  when  equally  representative  results  will  be  obtained  shall 
the  standard  gross  sample  be  used  instead  of  the  special  moisture 
sample  for  the  determination  of  total  moisture. 

11.  Sampling  Coke. — The  American  Society  for  Testing  Mate- 
rials adopted  in  1916  a  standard  method  for  sampling  foundry 
coke  which  is  quoted  below  from  the  A.  S.  T.  M.  Standards: 

I.  CHEMICAL  PROPERTIES  AND  TESTS.     (A)  SAMPLING 

1.  Each  carload,  or  its  equivalent,  shall  be  considered  as  a  unit. 

2.  (a)  The  sample  shall  be  taken  from  the  exposed  surface  of  the 
car,  by  knocking  off  with  a  hammer  a  piece  of  approximately  the  size 
of  a  walnut,  at  regular  intervals  of  18  in.  along  three  lines  running  from 
one  end  of  the  car  to  the  other.     One  of  these  lines  shall  pass  through 
the  center  of  the  car  and  the  other  two  lines  -shall  be  2  ft.  from  the 
respective  sides  of  the  car. 

(6)  The  intervals  of  sampling  along  the  three  lines  may  be  measured 
by  using  a  hammer  with  a  handle  18  in.  long,  breaking  off  a  piece  of 
coke  the  size  of  a  walnut  at  each  point  where  the  head  of  the  hammer 
rests,  regardless  of  the  appearance  of  the  particular  piece  that  happens 
to  occur  under  the  head  of  the  hammer. 

3.  The  total  quantity  of  sample  collected  in  the  above  manner  shall 
not  be  less  than  2  pecks. 

4.  When  the  total  moisture  content  is  not  to  be  determined  the  entire 
gross  sample  shall  be  crushed  to  pass  through  a  screen  having  4  meshes 
to  the  linear  inch,  under  such  conditions  as  shall  prevent  loss  or  the 
accidental  admixture  of  foreign  matter.     The  crushing  shall  be  done 
mechanically  with  a  jaw  crusher,  or  by  hand  on  a  chilled  iron  or  hard 
steel  plate  by  impact  of  a  chilled  iron  or  hard  steel  tamping  bar,  hammer 
or  sledge,  avoiding  all  rubbing  action,  otherwise  the  ash  content  of  the 
sample  will  be  materially  increased  by  the  addition  of  iron  from  the 
crushing  apparatus,  even  though  hardened  steel  or  chilled  iron  is  used. 

After  all  the  gross  sample  has  been  passed  through  the  4-mesh  screen, 
it  shall  be  mixed  on  a  strong,  closely  woven  cloth  about  5  ft.  square 
by  raising  successively  the  four  sides  of  the  cloth,  thus  rolling  the  sample 
about  until  thoroughly  mixed.  The  four  corners  of  the  cloth  shall  then 
be  gathered  up,  and  the  sample  shall  be  formed  in  a  conical  pile  and 
reduced  in  quantity  by  quartering  as  follows: 

The  cone  shall  be  flattened,  its  apex  being  pressed  down  so  that  each 


220  GAS  AND  FUEL  ANALYSIS 

quarter  contains  the  material  originally  in  it.  The  flattened  mass  shall 
then  be  divided  into  four  equal  quarters.  The  diagonally  opposite 
quarters  shall  then  be  removed  and  discarded  and  the  space  that  they 
occupied  brushed  clean.  The  two  remaining  quarters  shall  be  succes- 
sively mixed,  coned  and  quartered  on  the  cloth  as  before,  until  two 
opposite  quarters  shall  weigh  not  less  than  5  lb.,  which  shall  then  be 
placed  in  a  suitable  container  for  transportation  to  the  laboratory.  In 
case  duplicate  laboratory  samples  are  desired,  the  rejected  portions  of 
the  original  4-mesh  sample  shall  be  combined,  mixed  and  quartered 
down  to  a  similar  5-lb.  sample. 

5.  The  sample  prepared  by  the  above  method  may,  at  the  option  of 
the  purchaser,  be  used  for  an  approximate  moisture  determination. 
In  such  cases  the  gross  sample  shall  be  immediately  crushed  and  reduced 
to  the  5-lb.  laboratory  sample  as  rapidly  as  possible,  to  minimize  the 
loss  of  moisture.     The  container  for  shipment  to  the  laboratory  shall 
be  moisture- tight.     Since  the  sample  obtained  by  this  method  will 
usually  show  less  than  the  true  moisture  content  of  the  gross  sample, 
the  purchaser  shall  have  the  privilege  of  a  special  moisture  sample  as 
hereinafter  provided,  if  the  standard  sample  shows  more  than  3  per  cent, 
moisture. 

6.  The  special  moisture  sample  shall  consist  of  not  less  than  2  pecks 
of  walnut  size.     It  shall  be  taken  in  the  manner  described  in  Section  2, 
and  shall  be  placed,  immediately  after  collection,  in  a  moisture-tight 
container  for  transportation  to  the  laboratory.     The  car  shall  be  weighed 
at  the  time  the  special  moisture  sample  is  collected. 

7.  In  case  of  disagreement  between  buyer  and  seller,  an  independent 
chemist,  mutually  agreed  upon,  shall  be  employed  to  sample  and  analyze 
the  coke,  the  cost  to  be  borne  by  the  party  at  fault. 

The  resample  shall  be  taken  and  prepared  as  prescribed  in  the  fore- 
going sections,  except  that  the  minimum  quantity  of  gross  sample  shall 
be  not  less  than  1  bushel  in  volume,  taken  at  intervals  of  18  in.  in  six 
equidistant  lines  parallel  to  the  side  of  the  car. 


(B)  CHEMICAL  ANALYSIS 

8.  The  sample  received  at  the  laboratory  shall  be  prepared  for  analy- 
sis, and  the  percentage  of  moisture,  volatile  matter,  fixed  carbon,  ash, 
and  sulphur  shall  be  determined  as  specified  in  the  Standard  Methods 
for  Laboratory  Sampling  and  Analysis  of  Coke  of  the  American  Society 
for  Testing  Materials. 

9.  The  dry  coke  shall  not  exceed  the  following  limits  in  chemical 
composition : 


SAMPLING  COAL  221 

Volatile  matter not  over      2. 0  per  cent. 

Fixed  carbon not  under  86.0  per  cent. 

Ash not  over     12 . 0  per  cent. 

Sulphur not  over       1 . 0  per  cent. 

II.  REJECTION 

10.  (a)  In  case  the  original  standard  sample  was  taken  in  accordance 
with  Section  5  and  showed  more  than  3  per  cent,  moisture,  the  pur- 
chaser shall  have  the  option  of  taking  a  special  moisture  sample  accord- 
ing to  Section  6,  and  of  deducting  the  moisture  found  in  excess  of  3  per 
cent,  from  the  weight  of  coke  found  on  reweighing  the  car  at  the  time 
the  special  moisture  sample  was  taken. 

(&)  In  case  the  original  standard  sample  was  taken  with  special  regard 
to  moisture  in  accordance  with  Section  6,  the  purchaser  shall  have  the 
option  of  deducting  the  moisture  in  excess  of  3  per  cent,  from  the  weight 
of  coke,  provided  that  the  car  was  weighed  at  the  time  of  sampling. 

11.  Coke  which  fails  to  conform  to  the  limits  of  chemical  composition 
given  in  Section  9  will  be  rejected,  and  the  seller  shall  be  notified  within 
5  working  days  from  the  date  of  sampling. 

12.  Reliability  of  Samples. — It  is  evident  from  the  preceding 
paragraphs  that  it  is  possible  to  sample  crushed  coal  with  fair 
accuracy,  but  that  it  is  not  possible  to  sample  accurately  a  single 
lot  of  coal  containing  large  lumps  without  greater  expense  than 
is  usually  warranted.     The  error  is  largely  an  accidental  one 
due  to  the  inclusion  or  rejection  of  too  many  or  too  few  of  the 
larger  pieces  of  slate  in  the  sample.     There  may  also  be  a  sys- 
tematic error  if  care  has  not  been  taken  to  get  a  proper  propor- 
tion of  coarse  and  fine  coal.     So  far  as  the  error  is  accidental,  it 
will  diminish,  according  to  the  law  of  probabilities,  with  in- 
creasing number  of  samples,  so  that  although  any  one  sample 
may  be  in  error  by  3  per  cent.,  the  average  of  fifty  samples 
should  be  quite  accurate.     Contracts  which  involve  the  delivery 
of  coal  throughout  the  year  may  therefore  be  equitably  settled 
on  a  sliding  scale  based  on  analysis,  for  the  undue  premium  on 
one  shipment  will  be  counterbalanced  by  the  undue  penalty  on 
another  and  in  the  course  of  a  year  a  fair  average  will  have  been 
reached.     If  it  is  necessary  to  determine  accurately  the  value 
of  a  single  shipment,  greater  care  and  expense  is  necessary  than 
the  sum  at  issue  will  usually  warrant. 


CHAPTER  XV 
THE  CHEMICAL  ANALYSIS  OF  COAL 

1.  Introduction. — The  methods  used  in  analysis  of  coal  may 
be  grouped  into  two  main  divisions.     In  ultimate  analysis  the 
aim  is  to  report  as  accurately  as  may  be  the  percentages  of  the 
chemical  elements,  especially  carbon,  hydrogen,  nitrogen,  oxygen 
and  sulphur.     These  elements  are  reported  as  elements  without 
any  attempt  to  indicate  the  manner  in  which  they  are  combined 
in  the  coal.     This  method  of  analysis  is  scientifically  valuable  but 
finds  few  applications  in  technical  work.     In  proximate  analysis, 
on  the  other  hand,  the  attempt  is  made  to  group  the  constituents 
of  the  coal  according  to  certain  physical  properties  which  are 
technically  important  such  as  moisture,  volatile  matter  and  ash. 
This  method  of  analysis  is  of  great  commercial  importance. 
These  two  methods  of  analysis  are  applicable  to  all  forms  of 
solid  and  liquid  fuel — peat,  lignite,  bituminous  coal,  anthracite, 
coke,  petroleum,  tar,  etc. — with  slight  modifications  required  by 
the  physical  properties  of  the  fuel  being  investigated. 

2.  Proximate  Analysis. — The  usual  items  included  in  a  proxi- 
mate analysis  are  moisture,  volatile  matter,  fixed  carbon  and 
ash.     Sulphur  is  frequently  included  in  the  report,  but  is  deter- 
mined separately.     There  is  no  difficulty  in  comprehending  what 
is  meant  by  the  terms  moisture  and  ash,  although  the  actual 
determination  of  their  quantities  may  be  difficult.     The  expres- 
sions, volatile  matter  and  fixed  carbon,  require  explanation,  for 
they  are  merely  relative  terms  which  can  be  interpreted  only  by 
reference  to  certain  definite  conditions  of  analysis.     If  coal  be 
heated  to  redness  the  heat  will  decompose  a  portion  of  the  coal 
substance.     Part  of  this  decomposed  coal  will  be  evolved  as  a 
thick  black  smoke  which  will  burn  in  the  air  and  part  will  re- 
main behind  as  a  solid  coke  or  carbonaceous  residue.     If  tar  or 
petroleum  be  treated  in  this  manner  part  of  the  substance  will 
be  driven  off  in  the  same  form  in  which  it  existed  in  the  oil.     In 
the  case  of  coal  the  material  volatilized  is  formed  only  through 

222 


THE  CHEMICAL  ANALYSIS  OF  COAL  223 

the  decomposing  action  of  the  heat.  In  proximate  analysis  no 
attempt  is  made  to  separate  these  two  classes  of  products. 
Everything  which  is  evolved  in  the  process  is  called  "  volatile." 
The  residue  remaining  in  the  crucible  after  this  process  consists 
of  ash  and  a  material  which  is  largely  carbon  and  which  forms 
the  so-called  "  fixed  carbon."  The  percentages  reported  as  vola- 
tile matter  and  fixed  carbon  will  vary  with  every  modification 
of  the  conditions  of  analysis.  The  moisture  and  ash  are  also 
liable  to  vary  with  change  in  detail  of  method.  It  is  therefore 
very  important  that  all  chemists  should  use  the  same  method  in 
order  that  their  results  may  be  comparable.  The  standard 
method  is  given  in  Section  18  of  this  chapter. 

3.  Preliminary   Examination   of   Sample. — In   the   preceding 
chapter  on  Sampling  the  precautions  to  be  observed  in  taking 
the  initial  sample  and  in  subdividing  it  were  discussed.     There  is 
no  definite  point  where  the  sampler  is  to  stop  in  his  process  of 
subdivision  and  turn  the  material  over  to  the  chemist,  but  since 
the  sampler  is  in  general  a  field  worker  it  is  customary  to  con- 
sider his  work  as  ended  when  the  sample  has  been  reduced  in 
weight  sufficiently  to  allow  its  easy  transportation  to  the  labo- 
ratory.    It  is  advisable  that  the  sample  sent  to  the  laboratory 
should  weigh  from  3  to  5  Ib. 

The  chemist  receiving  a  sample  should  note  the  nature  of  the 
package  as  well  as  its  marks.  Coal  shipped  in  a  canvas  sack  or 
a  paper  carton  which  is  not  tight  will  almost  certainly  have 
changed  in  moisture  content  and  will  probably  have  lost  some 
of  its  finer  particles.  After  opening  the  package  the  net  weight 
of  sample  and  an  approximate  estimate  of  its  physical  condition 
should  be  recorded.  Information  as  to  whether  the  sample  as 
received  was  wet  or  dry,  and  whether  it  showed  evident  pieces 
of  slate  or  pyrite,  is  sometimes  of  importance.  The  size  of  the 
largest  lumps  relative  to  the  size  of  the  sample  shipped  will  give 
some  indication  of  the  care  which  has  been  used  in  the  prepara- 
tion of  the  sample.  The  chemist  should,  for  his  own  protection, 
state  in  his  report  when  the  sample  is  manifestly  a  non-repre- 
sentative one,  and  when  insufficient  care  has  been  exercised  in 
packing  it  for  shipment. 

4.  Air-drying. — It  is  inconvenient  to  handle  samples  of  coal 
which  are  wet,  since  they  clog  the  mills  and  cannot  be  mixed 


224 


GAS  AND  FUEL  ANALYSIS 


readily.  They  also  change  in  weight  rapidly  in  the  air.  It  is 
therefore  standard  practice  to  air-dry  the  sample.  This  may  be 
accomplished  by  spreading  in  a  thin  layer  in  a  tin  pan  placed  in 
a  warm  room  for  twenty-four  hours  or  longer  if  necessary  to 
bring  it  to  approximately  constant  weight.  The  process  may 
be  hastened  by  placing  the  samples  in  an  oven  such  as  is  used 
at  the  Bureau  of  Mines1  which  is  heated  to  not  over  100°  F.  and 


< -27 


4'4" - 

FIG.  48. — Oven  for  air-drying  coal  samples 

which  is  provided  with  forced  ventilation.  In  this  oven,  which 
is  illustrated  in  Fig.  48,  air  is  heated  by  a  Bunsen  burner  and 
circulated  by  a  small  electric  fan.  The  loss  in  weight  during  this 
process  is  reported  as  air-drying  loss.  All  analyses  are  made  on 
this  air-dried  coal  since  it  may  be  weighed  and  handled  in  the 
air  with  relatively  slight  change  of  weight.  There  is  evidence 
that  the  coal  slowly  changes  in  this  air-drying  process,  so  that  it 

1  Technical  Paper  8,  Bureau  of  Mines,  1912. 


THE  CHEMICAL  ANALYSIS  OF  COAL  225 

should  not  be  exposed  to  the  air  longer  than  necessary.  Porter1 
reports  that  Pittsburg  coal  on  drying  eight  days  at  35°  C.  ab- 
sorbed 0.17  per  cent,  of  oxygen  and  that  a  Wyoming  coal  similarly 
treated  absorbed  0.70  per  cent. 

5.  Grinding  and  Preserving  the  Sample  for  Analysis. — The 
sample  of  coal  which  has  been  air-dried  or  is  at  least  so  nearly 
air-dry  that  it  does  not  change  in  weight  in  the  air  rapidly  is  to 
be  crushed  and  subdivided  until  a  portion  of  50  or  60  grm.  is 
obtained  from  which  a  sample  of  1  grm.  may  be  taken  which 
shall  be  representative  of  the  whole  original  mass  of  coal.  Bailey 
in  the  reference  quoted  in  the  preceding  chapter  gives  the  follow- 
ing rules  for  subdivision  in  the  laboratory. 


Size  of  coal  mesh 

Should  not  be  divided  to 
less  than 

2 

8300  grm. 

4 

1100  grm. 

8 

120  grm. 

10 

55  grm. 

20 

3  grm. 

He  recommends  that  as  soon  as  the  sample  has  been  put  through 
an  8-mesh  sieve  that  it  be  all  crushed  to  60-mesh  or  finer. 

The  crushing  to  12-mesh  may  be  done  by  hand  in  a  mortar  or 
in  any  type  of  crusher  without  much  danger  of  injuring  the 
sample  if  it  is  done  rapidly.  It  is  necessary  to  take  precautions, 
however,  to  prevent  injury  to  the  sample  during  fine  grinding, 
for  finely  ground  coal  absorbs  oxygen  from  the  air  rapidly  and 
gives  off  water.  The  exact  nature  of  this  reaction  is  not  under- 
stood but  it  is  known  to  affect  the  heating  value  appreciably. 
This  change  is  accelerated  if  the  sample  becomes  heated  during 
the  fine  grinding.  For  this  reason  disc  grinders  should  be  used 
with  great  caution.  They  grind  rapidly  but  the  plates  get  hot, 
sometimes  hot  enough  to  start  destructive  distillation  of  the 
coal,  which  manifests  itself  by  a  tarry  odor.  If  the  disc  grinder 
is  used  the  plates  must  not  be  set  closer  than  necessary  and  the 
coal  must  be  fed  very  slowly.  The  best  method  of  finely  grind- 
ing coal  is  to  use  a  jar  mill.  This  consists  of  a  heavy  porcelain 


1  Jour.  Ind.  and  Eng.  Chem.,  5,  520  (1913). 
15 


226  GAS  AND  FUEL  ANALYSIS 

jar  provided  with  a  cover  which  may  be  clamped  tight  on  a 
rubber  gasket.  It  is  filled  about  one-third  full  of  round  flint 
pebbles  or  porcelain  balls  and  is  placed  in  a  frame  where  it  may 
be  rotated  at  the  rate  of  50  to  75  revolutions  per  minute.  The 
balls  tumbling  over  each  other  fall  with  sufficient  force  to  crack 
the  small  pieces  of  coal,  but  are  themselves  worn  off  to  only  a 
negligible  extent.  The  longer  the  coal  is  left  in  the  jar  the 
finer  it  becomes  and  it  is  easy  to  get  any  desired  degree  of  fine- 
ness. The  size  of  the  jar  required  and  the  diameter  of  the 
pebbles  will  vary  with  the  hardness  of  the  material  and  the 
size  of  the  lumps.  If  the  lumps  have  a  diameter  even  as  great  as 
one-fourth  that  of  the  pebbles,  some  of  the  lumps  may  become 
simply  rounded  balls  themselves  and  not  be  crushed  by  the  im- 
pact of  the  pebbles.  If  the  coal  has  been  put  through  a  10-  or 
12-mesh  sieve  before  going  into  the  ball  mill  a  jar  of  8  in.  internal 
diameter  and  with  pebbles  %  in.  or  1  in.  in  diameter  will  grind 
the  sample  properly,  provided  the  coal  does  not  occupy  over  one- 
sixth  of  the  volume  of  the  jar.  When  the  grinding  is  completed 
the  jar  is  emptied  onto  a  coarse  sieve  which  retains  the  balls. 
The  coal  should  be  tested  on  a  60-mesh  sieve  and  any  portions 
failing  to  pass  it  should  be  separately  ground  to  pass  an  80-mesh 
sieve  and  added  to  the  main  portion.  These  coarse  particles 
are  likely  to  be  slate  or  pyrites  and  therefore  especial  care  must 
be  taken  to  see  that  they  are  finely  ground  and  mixed  with  the 
main  sample.  A  coal  ground  to  pass  a  60-mesh  sieve  is  fine 
enough  to  make  a  1-grm.  sample  as  representative  of  the  lot  as 
the  various  intermediate  samples  were  of  the  initial  sample.  It 
is  not  desirable  to  grind  the  coal  much  finer  because  of  the  in- 
creased error  due  to  loss  of  moisture  and  absorption  of  oxygen 
by  the  finely  powdered  coal. 

This  finely  ground  sample  may  now  be  stored  as  a  whole  in 
a  fruit  jar  or  subdivided  and  an  amount  of  only  50  grm.  placed 
in  a  wide-mouthed  bottle  closed  with  a  rubber  stopper.  The 
bottle  should  be  filled  only  half  full  so  that  the  analyst  before 
weighing  out  his  sample  may  gently  shake  and  rotate  the  bottle 
to  mix  the  contents.  Pyrites  and  slate  tend  to  work  to  the 
bottom  of  a  sample  bottle  and  the  precaution  of  mixing  before 
taking  a  sample  should  never  be  omitted. 

Even  the  most  carefully  preserved  coals  deteriorate  in  time. 


THE  CHEMICAL  ANALYSIS  OF  COAL  227 

Parr1  has  shown  that  in  three  years'  storage  in  the  laboratory 
Eastern  coals  lose  in  heating  value  to  the  extent  of  0.5  to  1.5 
per  cent.,  while  Illinois  coals  deteriorate  to  the  extent  of  3  to  5 
per  cent.  Coals  which  are  to  be  kept  for  a  long  period  should 
be  sealed  as  nearly  air-tight  as  possible. 

6.  Moisture. — The  determination  of  moisture  in  coals  is  com- 
plicated by  the  change  which  the  coal  substance  itself  undergoes 
when  subjected  to  heat  and  exposure  to  the  air.  The  standard 
method  of  analysis  given  in  Section  18  prescribes  that  1  gram  of 
the  coal  shall  be  heated  for  one  hour  at  a  temperature  of  104° 
to  110°  C.  in  an  oven  through  which  a  current  of  dried  air  is 
circulated. 

The  errors  in  the  determination  of  moisture  in  coal  have  been 
studied  by  several  investigators,  among  them  Hillebrand  and 
Badger2  at  the  Bureau  of  Standards.  They  conclude  that  the 
most  nearly  correct  results  may  be  obtained  by  drying  in  vacua 
over  concentrated  sulphuric  acid  for  a  period  of  two  days  or  more. 
Results  obtained  by  a  method  similar  to  that  now  adopted  as  a 
standard  were  quite  consistent  and  in  most  cases  approximated 
those  obtained  in  a  vacuum.  Hulett3  proposes  a  method  for 
determining  the  true  moisture  in  coal  by  heating  in  a  vacuum 
so  controlled  that  water  is  removed  from  the  coal  as  fast  as 
liberated.  At  the  decomposition  temperature  of  the  coal  the 
curve  shows  a  sharp  break  due  to  evolution  of  synthetic  water 
and  this  point  marks  the  true  moisture  value.  The  Hulett 
method  gives  results  roughly  30  per  cent,  higher  than  the  stan- 
dard method.  Further  discussion  of  this  same  subject  is  found 
in  the  report  of  the  Committee  on  Standardization  of  Methods 
presented  to  the  Eighth  International  Congress  of  Applied 
Chemistry.4 

The  1913  report  of  the  Committee  on  Coal  Analysis  recom- 
mended that  sub-bituminous  and  lignitic  coals  are  to  be  dried  in 
a  stream  of  dry  carbon  dioxide  or  nitrogen.  After  the  samples 
were  dried  they  were  to  be  placed  in  a  vacuum  desiccator  which 

1  Eighth  Internal.  Congr.  Appl.  Chem.,  10,  225  (1912). 

2  Eighth  Internat.  Congr.  Appl.  Chem.,  10,  187  (1912). 

3  Mack  and  Hulett,  Am.  J.  Sci.,  43,  89  (1917). 
Hulett,  Mack,  and  Smyth,  Am.  J.  /Sci.,  45,  174  (1918). 

4  8th  Int.  Congr.  Applied  Chemistry,  25,  41  (1912). 


228  GAS  AND  FUEL  ANALYSIS 

was  then  exhausted  to  remove  absorbed  carbon  dioxide.  After 
exhaustion  the  desiccator  was  refilled  with  dry  air. 

7.  Volatile  Matter. — There  can  never  be  an  absolute  method 
for  the  determination  of  volatile  matter,  for  only  a  very  small 
proportion  of  the  material  evolved  from  coal  at  a  red  heat  was 
present  as  such  in  the  coal.  Most  of  this  volatile  material  is 
a  decomposition  product  whose  amount  varies  with  the  rate  of 
heating,  the  maximum  temperature  attained,  the  character  of 
the  flame,  the  size  of  the  crucible  and  other  conditions.  It  is 
necessary,  therefore,  in  a  standard  method  to  fix  every  possible 
variable  as  rigidly  as  possible. 

The  1899  method  of  the  American  Chemical  Society  is  as 
follows: 

"Place  1  grm.  of  fresh,  undried,  powdered  coal  in  a  platinum  cruci- 
ble, weighing  20  or  30  grm.  and  having  a  tightly  fitting  cover.  Heat 
over  the  full  flame  of  a  Bunsen  burner  for  seven  minutes.  The  crucible 
should  be  supported  on  a  platinum  triangle  with  the  bottom  six  to  eight 
centimeters  above  the  top  of  the  burner.  The  flame  should  be  fully 
twenty  centimeters  high  when  burning  free,  and  the  determination 
should  be  made  in  a  place  free  from  draughts.  The  upper  surface 
should  remain  covered  with  carbon.  To  find  'Volatile  Combustible 
Matter '  subtract  the  per  cent,  of  moisture  from  the  loss  found  here." 

More  recent  investigations  especially  by  Fieldner  and  Davis1 
and  by  Parr2  have  thrown  some  light  on  the  causes  of  variation. 
The  former  authors  working  in  the  laboratories  of  the  U.  S. 
Bureau  of  Mines  at  Pittsburgh  and  Washington  found  that  the 
carburetted  water  gas  of  Washington  gave  a  maximum  tempera- 
ture of  970°  C.  within  the  crucible  which  was  120°  hotter  than 
could  be  obtained  with  the  coal  gas  of  Pittsburgh  or  with  natural 
gas  burned  under  favorable  conditions.  They  summarize  the 
results  of  their  experiments  as  follows: 

"Two  laboratories  are  likely  to  vary  2  per  cent,  in  volatile  matter, 
both  using  the  official  method  (of  1899).  The  percentage  of  volatile 
matter  obtained  from  the  same  sample  of  coal  varies  with  the  tempera- 
ture and  rate  of  heating.  This  is  not  sufficiently  defined  by  height 
of  flame.  Temperatures  ranging  from  760°  C.  to  890°  C.  may  be  at- 
tained with  a  20-cm.  natural  gas  flame,  when  the  gas  pressure  is  varied 

1  Jour.  Ind.  and  Eng.  Chem.,  2,  304  (1910). 

2  Jour.  Ind.  and  Eng.  Chem.,  3,  900  (1911). 


THE  CHEMICAL  ANALYSIS  OF  COAL  229 

from  1  to  13  in.  of  water;  variations  of  2  per  cent,  volatile  matter  are 
thus  produced.  Differences  in  type  and  sizes  of  burner  influence  re- 
sults from  0.3  to  1.5  per  cent.  Polished  crucibles  become  hotter  and 
yield  about  1  per  cent,  more  volatile  matter  than  dull  gray  ones.  Labo- 
ratories using  natural  gas  are  apt  to  get  results  on  volatile  matter  that 
are  considerably  lower  than  those  using  coal  gas,  unless  the  following 
precautions  are  observed:  (1)  Gas  should  be  supplied  to  the  burner  at 
a  pressure  of  not  less  than  10  in.  of  water.  (2)  Natural  gas  burners 
admitting  an  ample  supply  of  air  should  be  used.  (3)  Gas  and  air 
should  be  regulated  so  that  a  flame  with  a  short,  well-defined  inner 
cone  is  produced.  (4)  The  crucibles  should  be  supported  on  platinum 
triangles  and  kept  in  well-polished  condition." 

The  1913  report  of  the  Committee  on  Coal  Analysis  recom- 
mends the  following  two  alternate  methods  for  the  determination 
of  volatile  matter. 

"It  is  recommended  that  for  volatile  matter  determinations  a  10-grm. 
platinum  crucible  be  used  having  a  capsule  cover,  that  is,  one  which 
fits  inside  of  the  crucible  and  not  on  top.  The  crucible  with  1  grm.  of 
coal  is  placed  in  a  muffle  maintained  at  approximately  950°  C.  for  seven 
minutes.  With  a  muffle  of  the  horizontal  type,  the  crucible  should  not 
rest  on  the  floor  of  the  muffle  but  should  be  supported  on  a  platinum 
or  nichrome  triangle  bent  into  a  tripod  form.  After  the  more  rapid 
discharge  of  the  volatile  matter,  well  shown  by  the  disappearance  of 
the  luminous  flame,  the  cover  should  be  tapped  lightly  to  more  per- 
fectly seal  the  cover  and  thus  guard  against  the  admission  of  air. 

"One  gram  of  coal  is  placed  in  a  platinum  crucible  of  approximately 
20  c.c.  capacity  (35  mm.  in  diameter  at  the  top  and  35  mm.  high). 
The  crucible  should  have  a  capsule  cover  which  will  readily  adjust 
itself  to  the  inside  upper  surface  of  the  crucible.  The  crucible  is  placed 
in  the  flame  of  a  Meker  burner,  size  No.  4,  having  approximately  an 
outside  diameter  at  the  top  of  25  mm.  and  giving  a  flame  not  less  than 
15  cm.  high.  The  temperature  should  be  from  900°  to  950°  C.  deter- 
mined by  placing  a  thermocouple  through  the  perforated  cover  which 
for  this  purpose  may  be  of  nickel.  The  junction  of  the  couple  should 
be  placed  in  contact  with  the  center  of  the  bottom  of  the  crucible. 
Or  the  temperature  may  be  indicated  by  the  fusion  of  pure  potassium 
chromate  in  the  covered  crucible  (fusion  of  K2CrOi,  940°  C.).  The 
crucible  is  placed  in  the  flame  about  1  cm.  above  the  top  of  the  burner 
and  the  heating  is  continued  for  seven  minutes.  After  the  main  part 
of  the  gases  has  been  discharged  the  cover  should  be  tapped  into  place 
as  above  described, 


230  GAS  AND  FUEL  ANALYSIS 

"For  lignites  a  preliminary  heating  of  five  minutes  is  carried  out, 
during  which  time  the  flame  of  the  burner  is  played  upon  the  bottom 
of  the  crucible  in  such  a  manner  as  to  bring  about  the  discharge  of 
volatile  matter  at  a  rate  not  sufficient  to  cause  sparking.  After  the 
preliminary  heating  the  crucible  is  placed  in  the  full  burner  flame  for 
seven  minutes  as  above  described." 

The  present  standard  method  as  given  in  Section  18  prescribes 
that  the  volatile  matter  shall  be  determined  in  a  vertical  electric 
tube  furnace  or  a  muffle  furnace. 

8.  Ash. — The  ash  of  coal  is  generally  defined  as  the  mineral 
residue  remaining  after  complete  combustion.  The  present 
standard  method  is  given  in  Section  18.  The  1899  method  of 
the  American  Chemical  Society  is  as  follows: 

"Burn  the  portion  of  powdered  coal  used  for  the  determination  of 
moisture,  at  first  over  a  very  low  flame,  with  the  crucible  open  and 
inclined,  till  free  from  carbon.  If  properly  treated,  this  sample  can 
be  burned  much  more  quickly  than  the  dense  carbon  left  from  the  de- 
termination of  volatile  matter.  It  is  advisable  to  examine  the  ash  for 
unburned  carbon  by  moistening  it  with  alcohol." 

The  errors  attending  the  determination  of  ash  have  been 
studied  very  carefully  by  Parr,1  who  has  shown  that  90  per  cent, 
of  the  Illinois  coals  carry  as  much  as  0.2  per  cent,  of  calcium 
carbonate,  nearly  half  have  more  than  1  per  cent.,  one-fifth  have 
more  than  2  per  cent.,  a  considerable  number  over  4  per  cent.,  and 
a  few  isolated  cases  carry  over  10  per  cent,  of  calcium  carbonate 
in  the  raw  coal.  Since  decomposition  of  CaCOs  is  rapid  at 
900°  C.  and  evident  at  600°  it  is  apparent  that  in  coals  of  this 
type  care  must  be  taken  to  determine  the  actual  amount  of 
CaCOs  present.  Parr  has  also  shown  that  sulphate  in  the  form 
of  ferrous  or  ferric  sulphate  is  present  in  fresh  coal  in  amounts 
varying  from  a  few  tenths  up  to  1  per  cent,  and  that  this  amount 
increases  rapidly  in  the  finely  ground  portions  of  the  laboratory 
sample.  With  coals  high  in  lime  this  sulphate  on  ignition  for 
ash  probably  becomes  calcium  sulphate,  as  does  also  the  sulphur 
of  pyrites. 

The  1913  report  of  the  Committee  on  Coal  Analysis  recom- 
mends the  following  method  for  the  determination  of  ash. 

1  Jour.  Ind.  and  Eng.  Chem.,  5,  523  (1913).  111.  State  Geological  Survey, 
Bui.  16,  p.  242. 


THE  CHEMICAL  ANALYSIS  OF  COAL  231 

"Unless  the  coal  is  of  a  type  known  to  be  free  from  carbonate  the 
amount  of  carbon  dioxide  must  be  determined.  A  5-grm.  sample, 
recently  boiled  distilled  water  and  dilute  hydrochloric  acid  are  em- 
ployed, making  use  of  any  convenient  apparatus  for  collecting,  absorb- 
ing and  measuring  accurately  the  carbon  dioxide  discharged  from  the 
coal.  It  is  most  convenient  to  obtain  the  factor  as  in  the  form  of 
carbon. 

"One  gram  of  coal,  either  freshly  weighed  or  that  which  has  been 
used  for  the  moisture  determination,  is  ignited  in  a  shallow  capsule  or 
porcelain  crucible  by  placing  directly  in  a  muffle  maintained  at  a  dull  or 
cherry-red  temperature  between  700  and  750°  C.  and  retained  at  this 
temperature  for  20  or  30  minutes  or  until  all  of  the  carbon  is  burned  out. 
The  capsule  is  cooled  in  a  desiccator  and  weighed.  In  the  absence  of  a 
muffle  the  desired  temperature  may  be  obtained  by  placing  the  capsule 
at  first  just  above  the  tip  of  a  Bunsen  flame  turned  down  to  about  2 
or  3  in.  in  height.  After  the  larger  part  of  the  carbon  is  burned  off  in 
this  manner  the  flame  is  increased  so  that  the  tip  comes  well  into 
contact  with  the  bottom  of  the  capsule. 

"For  coals  having  carbon  dioxide  present  in  an  amount  to  exceed  0.2 
per  cent.,  the  ash  after  cooling  is  moistened  with  a  few  drops  of  sulphuric 
acid  (diluted  1  :  1)  and  again  carefully  brought  up  to  750°  C.  and  re- 
tained at  that  temperature  for  three  to  five  minutes.  The  capsule  is 
cooled  in  a  desiccator  and  weighed.  Three  times  the  equivalent  of 
carbon  present  as  carbon  dioxide  is  subtracted  from  the  ash  as  weighed 
in  order  to  restore  the  weight  of  the  calcium  sulphate  formed  to  the 
equivalent  of  calcium  carbonate. " 

The  appearance  of  the  ash  gives  some  indication  of  its  fusing 
point  and  hence  its  tendency  to  form  clinkers.  The  largest  con- 
stituents in  ash  are  silica  and  alumina,  all  of  whose  compounds 
have  relatively  high  melting-point  and  are  white  in  color.  Iron 
oxide  colors  ash  red  and  reduces  the  melting-point  of  the  alumina 
silica  series  markedly.  Therefore  a  red  ash  indicates  low  melting- 
point  and  trouble  with  clinker  while  a  white  ash  usually  indicates 
high  melting-point.  This  rule  fails  with  coals  such  as  those  from 
Illinois  which  carry  material  amounts  of  lime,  for  the  lime  reduces 
the  melting-point  without  giving  a  color.  However,  the  Illinois 
coals  usually  carry  enough  iron  to  give  a  red  color  as  well. 

A  long  series  of  tests  conducted  by  the  Bureau  of  Mines  has 
resulted  in  the  development  of  a  method  for  determining  the 
fusibility  of  coal  ash  which  has  been  adopted  by  the  American 


232  GAS  AND  FUEL  ANALYSIS 

Society  for  Testing  Materials.1  In  this  method  the  finely  ground 
and  thoroughly  oxidized  ash  is  made  into  a  plastic  mass  with 
dextrin  and  formed  into  cones.  These  cones  are  heated  in  a  spe- 
cial furnace  and  in  a  reducing  atmosphere  until  the  softening 
point  is  reached.  An  analyst  should  check  his  own  results  within 
30°  C.  and  should  check  a  different  analyst  within  50°  C. 

9.  Fixed  Carbon. — -Fixed  carbon  is  obtained  by  adding  to- 
gether the  weights  of  moisture,  volatile  matter  and  ash  and  sub- 
tracting this  sum  from  the  weight  of  the  initial  sample.     Since 
the  amount  of  fixed  carbon  is  obtained  by  difference,  proximate 
analyses  of  coal  always  add  up  to  an  even  100  per  cent.     The 
percentage  of  fixed  carbon  plus  ash  gives  a  fair  indication  of  the 
amount  of  coke  which  would  be  obtained  from  a  coal.     An  indi- 
cation of  the  quality  of  the  coke  may  be  obtained  from  an  exam- 
ination of  the  residue  remaining  after  the   determination   of 
volatile  matter.     Good  coking  coals  give  a  button  of  hard  dense 
coke.     Feebly  coking  coals  give  a  cracked  and  weak   button 
while  non-coking  anthracites  and  lignites  give  a  powdery  or 
granular  residue. 

10.  Sulphur. — The  estimation  of  sulphur  is  usually  considered 
as  part  of  a  proximate  analysis  although  it  is  estimated  separately 
and  its  percentage  is  not  included  in  the  100  per  cent,  formed  by 
the  sum  of  the  moisture,  volatile  matter,  fixed  carbon  and  ash. 
Sulphur  usually  exists  in  coal  as  pyrites  FeS2,  but  part  of  it  may 
exist  in  combination  with  carbon  compounds,  part  even  as  free 
sulphur  and  especially  in  weathered  coals  as  calcium  sulphate 
or  sulphate  of  iron.     No  attempt  is  ordinarily  made  to  distinguish 
between  these  various  forms  of  sulphur,  although  Powell  and 
Parr2  have  described  methods  for  separating  sulphate  sulphur, 
pyrite    sulphur,    humus,    and    resinic    sulphur.     In    the    usual 
methods  of  analysis,  the  coal  is  treated  with  an  agent  which 
finally  brings  all  forms  of  sulphur  into  a  soluble  sulphate  form. 
This  is  then  precipitated  as  barium  sulphate  and  calculated  back 
to  sulphur.     The  method  recommended  in  1899  by  the  American 
Chemical  Society  was  a  modification  of  that  proposed  by  Eschka 
in  1874. 

1  Fieldner,  Hall  and  Field,  Bui.  129,  Bureau  of  Mines  (1918). 
Proc.  Am.  Soc.  for  Testing  Mat.,  1919,  1,  756  (1919). 

2  Bui.  Am.  Inst.  Mining  Met.  Eng.,  1919,  2041. 


THE  CHEMICAL  ANALYSIS  OF  COAL  233 

The  committee  on  Coal  Analysis  in  its  report  made  in  1913 
adopts  the  report  presented  by  Barker1  permitting  the  use  of 
three  alternative  methods  which  have  shown  themselves  to  be 
accurate.  The  methods  are: 

(a)  the  Eschka  method. 

(6)  the  Atkinson  method  of  fusion  with  sodium  carbonate. 

(c)  the  method  of  fusion  with  sodium  peroxide 

The  Eschka  method  is  recommended  in  substantially  the  same 
form  as  in  the  standard  method  of  1899.  The  substitution  of 
copper  oxide  for  magnesium  oxide  in  the  method  gives  more 
rapid  combustion  but  it  has  been  objected  to  on  the  ground  that 
the  black  specks  of  copper  oxide  look  so  much  like  free  carbon 
that  it  is  difficult  to  tell  when  the  coal  is  completely  burned. 
Details  of  the  Eschka  method  are  given  in  Section  18. 

The  Peroxide  Fusion  Method. — -The  decomposition  of  coal  by 
fusion  with  sodium  peroxide  was  first  proposed  by  Parr2  for 
calorimetric  purposes.  The  reaction  was  adapted  to  the  esti- 
mation of  sulphur  by  Sundstrom3  and  later  modified  by  Pennock 
and  Morton,4  and  Parr.5  The  method  is  entirely  reliable  and 
is  much  more  rapid  than  the  Eschka  method. 

When  a  mixture  of  a  dry  combustible  substance  and  sodium 
peroxide  in  proper  proportions  is  ignited  by  a  hot  iron  wire,  the 
mass  fuses  with  very  little  spattering  and  the  sulphur,  no  matter 
what  its  initial  form  of  combination,  is  converted  to  a  soluble 
sodium  sulphate.  If  the  coal  is  damp  or  the  proportions  are  not 
correct  there  may  be  violent  spattering  so  the  reaction  should 
be  carried  out  in  a  closed  vessel.  The  residue  from  the  deter- 
mination of  heating  value  in  the  Parr  calorimeter  is  of  course 
available  at  once  for  the  estimation  of  sulphur.  Where  a  separate 
combustion  for  sulphur  is  to  be  made  a  simple  crucible  of  steel 
or  brass  provided  with  a  perforated  cover  which  may  be  clamped 
in  place  is  used,  as  shown  in  Fig.  49.  For  a  charge  of  0.7  grm. 
bituminous  coal  about  16  grm.  of  sodium  peroxide  are  required 

1  Jour.  Ind.  and  Eng.  Chem.,  5,  524  (1913). 

2  J.  Am.  Chem.  Soc.,  22,  646  (1900). 
3J.  Am.  Chem.  Soc.,  25,  184  (1903). 

4  J.  Am.  Chem.  Soc.,  25,  1265  (1903). 

5  J.  Am.  Chem.  Soc.,  30,  767  (1908). 


234 


GAS  AND  FUEL  ANALYSIS 


while  for  the  same  weight  of  coke  or  anthracite  about  12  grm.  of 
peroxide  are  best.  The  charge  is  mixed,  the  cover  clamped  on 
and  the  crucible  placed  on  a  support  in  a  pan  of  water,  so  that 
its  lower  half  is  immersed  and  yet  there  is  free  circulation  of 
water  around  the  bottom.  The  charge  is  fired  by  a  stiff  iron 
wire  which  is  heated  to  redness  and  thrust  through  the  hole  in 
the  cover.  If  the  reaction  proceeds  properly  almost  no  flame 
will  issue  from  the  hole.  If  the  proportions  are  not  correct  there 

may  be  considerable  spattering  so 
that  the  operator  should  stand  at 
arms  length  from  the  crucible  when 
inserting  the  wire.  If  the  first  explo- 
sion is  too  violent,  add  more  sodium 
peroxide  which  acts  as  a  diluent.  If, 
on  the  other  hand,  combustion  has 
been  incomplete  as  shown  by  soot  on 
the  inside  of  the  lid  of  the  crucible, 
decrease  the  amount  of  sodium  perox- 
ide on  the  next  attempt.  If  there  is 
difficulty  in  obtaining  ignition  as  is 
sometimes  the  case  with  coke  and 
especially  with  ashes,  add  an  acceler- 
ator. Parr  recommends  the  following 
fusion  mixture:  10  grm.  sodium  peroxide,  0.5  grm.  potassium 
chlorate,  0.5  grm.  benzoic  acid. 

To  dissolve  the  fused  mass,  place  the  crucible  and  cover  in 
about  200  c.c.  of  distilled  water.  Rinse  off  the  crucible,  acidify 
slightly  with  HC1,  filter  out  any  insoluble  matter  and  proceed 
with  precipitation  of  BaSO4  as  in  the  Eschka  method. 

The  details  of  the  Atkinson  method  as  recommended  by  the 
Committee  on  Coal  Analysis  are  as  follows: 

The  Atkinson  Method.1 — "Thoroughly  mix  on  glazed  paper  1  grm. 
of  the  laboratory  sample  of  coal  with  7  grm.  of  dry  sodium  carbonate 
and  spread  evenly  over  the  bottom  of  a  shallow  platinum  or  porcelain 
dish.  Place  on  a  triangle  slightly  elevated  above  the  bottom  of  a  cold 
muffle.  Raise  the  temperature  of  the  muffle  gradually  until  a  tem- 
perature of  650°  to  700°  C.  (dull  red  heat)  has  been  obtained  in  half 
an  hour  and  maintain  this  temperature  for  ten  or  fifteen  minutes. 


FIG.  49. — Crucible  for 
peroxide  fusion. 


1  /.  Am.  Chem.  Soc.,  21,  1128  (1899). 


THE  CHEMICAL  ANALYSIS  OF  COAL  235 

The  sodium  carbonate  should  not  sinter  or  fuse.  The  mixture  should 
not  be  stirred  during  the  heating  process.  When  the  dish  has  cooled 
sufficiently  to  handle,  the  matter  should  be  examined  for  black  particles 
of  unburned  carbon  and  in  case  such  indications  of  incompleteness  of 
the  process  appear,  the  dish  should  be  replaced  and  heated  for  a  short 
time.  When  all  carbon  is  burned,  remove  the  dish  and  digest  the  con- 
tents with  100  to  125  c.c.  of  warm  water.  Allow  the  insoluble  matter 
to  settle,  decant  through  a  filter  and  wash  several  times  by  decantation. 
Transfer  to  the  filter,  adding  a  few  drops  of  a  solution  of  pure  sodium 
chloride,  if  the  insoluble  matter  tends  to  pass  through  the  filter.  The 
washing  should  be  continued  until  the  filtrate  shows  no  alkaline  reac- 
tion. Make  the  filtrate  slightly  acid' with  sufficient  concentrated  hydro- 
chloric acid  and  precipitate  the  sulphates  with  barium  chloride  as  de- 
scribed under  the  Eschka  method.  No  oxidizing  agent  is  required." 

Sulphur  may  also  be  determined  in  the  water  rinsed  from 
the  bomb  calorimeter  after  a  calorimetric  determination,  pro- 
vided proper  care  is  taken  in  the  combustion.  Regester1  has 
shown  that  it  is  necessary  to  have  a  pressure  of  20  atmospheres 
and  a  nitrogen  content  of  6  per  cent,  in  the  bomb  before  ignition 
to  ensure  oxidation  of  the  SOz.  This  is  discussed  further  in 
Chapter  XVI.  The  sulphuric  acid  cannot  be  determined  by 
direct  titration  since  some  nitric  acid  is  also  formed  and  some 
of  the  acid  may  have  been  neutralized  by  reaction  with  the 
metal  of  the  bomb  or  with  particles  of  ash  which  were  spattered 
out  during  combustion.  The  bomb  should  be  rinsed  out  very 
thoroughly  with  hot  water.  Even  then,  Regester  shows  that 
the  results  on  sulphur  are  usually  low  by  from  3  to  5  per  cent. 

Parr2  has  developed  a  rapid  photometric  method  for  the  de- 
termination of  sulphur  in  coal.  The  residue  from  the  fusion 
with  sodium  peroxide  is  dissolved,  acidified,  diluted,  and  pre- 
cipitated cold  with  a  mixture  of  barium  chloride  and  oxalic  acid. 
The  precipitated  barium  sulphate  is  in  a  very  finely  divided 
condition  so  that  it  does  not  settle  readily.  The  photometer 
consists  of  a  graduated  tube  of  special  design  which  rests  upon 
a  diaphragm  below  which  is  a  candle  flame.  The  emulsion  of 
BaSO4  and  solution  is  slowly  poured  into  this  photometer  until 

1  Jour.  Ind.  and  Eug.  Chem.,  6,  812  (1914). 

2  Jour.  Am.  Chem.  Soc.,  26,  1139  (1904);  Jour.  Ind.  and  Eng.  Chem.,  1, 
689  (1909). 


236  GAS  AND  FUEL  ANALYSIS 

the  sharp  outline  of  the  flame  disappears.  The  height  of  solu- 
tion in  the  photometer  tube  gives,  by  reference  to  a  special  table, 
the  per  cent,  of  sulphur  in  the  coal.  Results  on  35  coals  quoted 
by  Parr  show  good  agreement  with  gravimetric  methods. 

11.  Ultimate  Analysis. — -Carbon  and  Hydrogen. — Carbon  and 
hydrogen  in  coal  and  coke  are  determined  as  is  usual  in  the  ulti- 
mate analysis  of  organic  compounds,  by  combustion  in  a  stream 
of  dry  and  pure  oxygen  and  absorption  of  the  resulting  carbon 
dioxide  and  water.  The  analysis  is  a  difficult  one  and  should 
not  be  attempted  by  one  who  has  not  had  practice  in  the  general 
method.  If  it  is  necessary  for  an  analyst  without  training  in 
this  particular  line  to  undertake  such  an  analysis  he  should  prac- 
tice on  the  ultimate  analysis  of  such  pure  compounds  as  sugar 
and  benzoic  acid  until  he  has  attained  proficiency.  Detailed 
directions  for  these  determinations  in  coal  are  given  in  Technical 
Paper  8  of  the  Bureau  of  Mines.  The  standard  method  is  given 
in  Section  18. 

In  a  determination  of  the  heating  value  of  coal  in  a  bomb 
calorimeter,  there  is  complete  oxidation  of  the  carbon  to  carbon 
dioxide  and  of  the  hydrogen  to  water.  An  absorption  train 
may  be  connected  to  the  bomb  and  the  gases  allowed  to  bubble 
slowly  through  it.  After  the  pressure  in  the  bomb  has  fallen 
to  that  of  the  atmosphere  the  bomb  may  be  immersed  in  a  dish 
of  hot  water  and  suction  applied  to  the  absorption  train.  It  is 
in  this  way  possible  to  estimate  the  carbon  dioxide  and  water 
formed  in  the  combustion.  Kroeker1  proposes  a  bomb  which 
has  an  inlet  and  an  outlet  valve  so  that  dry  and  pure  air  may  be 
passed  through  the  bomb  after  the  pressure  has  been  relieved. 
The  method  is  capable  of  giving  good  results  in  skilled  hands. 
Great  care  must  be  taken  to  keep  the  packing  on  the  oxygen 
valves  in  perfect  condition  as  otherwise  part  of  the  products  of 
combustion  will  escape  during  the  slow  process  of  emptying  the 
bomb.  There  is  also  a  minor  error  due  to  the  oxidation  of  some 
of  the  nitrogen  to  form  nitric  acid  which  is  reported  as  carbon 
dioxide. 

Parr2  has  proposed  a  gas  volumetric  method  of  determining 
carbon  from  the  residue  of  the  peroxide  fusion  in  the  Parr  calor- 

1  Zeit.  d.  Vereinsf.  d.  Rubenzuckerindustrie,  46,  177  (1896). 

2  University  of  Illinois  Bulletin  Vol.  1,  No.  20  (1904). 


THE  CHEMICAL  ANALYSIS  OF  COAL  237 

imeter.  The  residue  consisting  largely  of  Na2C03  and  Na2O2  is 
dissolved  in  water  and  treated  with  acid.  Carbon  dioxide  and 
oxygen  are  evolved  and  the  carbon  dioxide  is  estimated  by  ab- 
sorption. There  are  a  number  of  minor  sources  of  error  which 
make  it  difficult  to  get  accurate  results  by  this  method.  Sodium 
peroxide  both  dry  and  in  solution  readily  absorbs  carbon  dioxide 
from  the  air  and  care  is  necessary  in  order  to  keep  the  correction 
factors  constant.  Difficulty  has  also  been  experienced  in  com- 
pletely boiling  off  the  carbon  dioxide  from  the  solution. 

12.  Nitrogen. — The  chief  value  attaching  to  a  knowledge  of 
the  per  cent,  of  nitrogen  in  a  coal  is  the  indication  which  it  is 
believed  to  give  of  the  amount  of  ammonia  which  the  coal  will 
yield  on  destructive  distillation.     No  attempt  is  usually  made 
to  distinguish  between  the  various  forms  in  which  nitrogen  may 
exist  in  coal.     The  total  nitrogen  is  best  determined  by  the 
Kjehldahl  method  or  one  of  its  modifications  as  regularly  used 
in  the  ultimate  analysis  of  organic  compounds.     Details  are 
given  in  Technical  Paper  8  of  the  Bureau  of  Mines.     The  stand- 
ard method  is  given  in  Section  18. 

13.  Phosphorus. — Phosphorus  is  usually  determined  only  in 
fuels  which  are  to  be  used  for  metallurgical  processes  where  the 
fuel  is  to  come  in  direct  contact  with  the  metal.     The  standard 
method  of  analysis  is  given  in  Section  18. 

14.  Oxygen. — There  is  no  direct  method  for  the  estimation 
of  oxygen  in  coal.     In  an  ultimate  analysis  the  percentages  of 
carbon,  hydrogen,  nitrogen,  sulphur  and  ash  are  added  and  the 
difference  between  this  sum  and  100  per  cent,  is  called  oxygen. 
It  is  thus  apparent  that  any  errors  in  the  estimation  of  the  other 
constituents  are  reflected  in  the  figure  for  oxygen  and  that 
therefore  this  figure  is  to  be  regarded  as  the  least  significant  of 
the  analysis.     A  formula  which  makes  correction  for  some  of 
the  errors  is  given  in  Section  18. 

15.  Methods  of  Reporting  Analyses.— The  analysis  is  usually 
made  on  the  air-dried  sample  since  the  sample  in  this  form  is 
least  liable  to  change.     The  original  figures  obtained  by  the 
analyst  will  therefore  be  for  coal  in  this  form.     He  may  now 
take  into  account  the  moisture  lost  in  air-drying  and  calculate 
the  analysis  to  a  basis  of  coal  "as  received,"  he  may  mathemat- 
ically eliminate  all  the  water  and  report  as  "Coal  free  from  Mois- 


238 


GAS  AND  FUEL  ANALYSIS 


ture,"  or  he  may  by  calculation  eliminate  both  the  moisture  and 
ash  and  report  as  "  Coal  free  from  Moisture  and  Ash." 

Numerous  attempts  have  been  made  to  calculate  "true  coal"1 
or  "coal  substance"  by  elimination,  in  addition  to  the  moisture 
and  ash,  of  water  of  hydration  contained  in  shale,  and  carbon  diox- 
ide contained  in  carbonates  of  the  ash — both  of  which  are  driven 
off  in  whole  or  in  part  with  the  volatile  matter  whereas  they 
really  belong  to  the  ash.  Such  corrections  are  difficult  to  apply 
and  are  not  often  made  in  technical  work.  In  any  event  the 
data  reported  should  be  sufficient  to  allow  a  recalculation  of  the 
results  to  any  other  basis.  Ordinarily  the  air-drying  loss  and 
analysis  of  air-dried  coal  are  reported  since  they  are  the  figures 
actually  obtained  by  the  analyst  and  in  addition  whatever  other 
forms  of  report  may  be  called  for.  The  following  analysis  of  a 
Pittsburg  coal  shows  the  form  of  report. 

PERCENTAGE  COMPOSITION  OF  COAL 


Proximate  analysis 

Air-dried 

As  received 

Calculated 
moisture- 
free 

Calculated 
moisture  and 
ash-free 

Maoist  ure 

1  07 

3  94 

Volatile  matter  

34.55 

33.55 

34.93 

37  13 

Fixed  carbon  

58  51 

56.81 

59  14 

62  87 

Ash 

5  87 

5  70 

5  93 

100.00 

100.00 

100.00 

100.00 

Ultimate  analysis 
Hydrogen  

5.16 

5  33 

5  09 

5  41 

Carbon 

79  52 

77  21 

80  38 

85  44 

Nitrogen  

1.41 

1.37 

1.43 

1.52 

Oxvcen.  . 

6.97 

9.35 

6.09 

6.48 

Sulphur 

1  07 

1  07 

1  08 

1  15 

Ash  

5.87 

5.70 

5.93 

100.00 

100.00 

100.00 

100.00 

Air-drying  loss  

2.90 

16.  Accuracy  of  Results. — It  will  be  evident  from  a  consider- 
ation of  this  chapter  and  the  preceding  one  on  sampling  that  the 

1  See  The  Chemical  Examination  of  Water,  Fuel,  Flue  Gases  and  Lubri- 
cants, by  S.  W.  Parr. 


THE   CHEMICAL  ANALYSIS  OF  COAL 


239 


error  in  sampling  is  likely  to  be  larger  than  the  error  of  analysis. 
The  Joint  Committee  on  Coal  Analysis  in  its  1913  report  esti- 
mates the  allowable  variations  under  its  methods  of  analysis  as 
follows : 


Same  analyst, 
per  cent. 

Different 
analysts, 
per  cent. 

l^toisture  under  5  per  cent            

0.2 

0.3 

Moisture  over  5  per  cent                   

0  3 

0  5 

Volatile  matter,  bituminous  coals  
Volatile  matter  licnites 

0.5 
1  0 

1.0 
2  0 

Ash  no  carbonates  present  

0.2 

0.3 

Ash  carbonates  present                            .  . 

0.3 

0.5 

Ash   more  than  12  per  cent 

0  5 

1  0 

Sulphur  in  coal              

0.05 

0.1 

Sulohur.  in  coke.  . 

0.03 

0.05 

The  greatest  variation  is  in  the  volatile  matter  and  when  a  con- 
tract is  to  be  awarded  in  which  an  accurate  determination  of 
volatile  matter  is  demanded,  it  is  advisable  for  the  purchaser 
and  the  bidder  to  jointly  analyze  a  single  sample  of  coal  and 
harmonize  their  differences  in  analytical  procedure  before  the  con- 
tract is  awarded.  Lord,1  from  his  wide  experience,  states  that  in 
ultimate  analysis  the  accuracy  can  be  safely  stated  as  within 
0.05  per  cent,  in  the  case  of  hydrogen,  perhaps  0.3  per  cent,  on 
carbon,  0.03  per  cent,  on  nitrogen  and  0.05  per  cent,  on  sulphur. 
Davis  and  Fairchild2  have  mathematically  investigated  the  prob- 
able errors  in  coal  analysis  using  the  method  of  least  squares 
and  concluded:  "It  would  seem,  then,  that  the  limits  allowed 
by  the  committee  on  coal  analysis  of  the  American  Society  for 
Testing  Materials  are  not  limits  outside  which,  with  ordinary 
care,  determinations  could  never  fall;  it  would  seem  rather  that 
the  committee  means  to  designate  limits  within  which  a  large 
percentage  of  the  errors  will  fall." 

17.  Slate  and  Pyrites. — It  is  frequently  desirable  to  determine 
how  much  of  the  pyrites  and  slate  is  in  a  form  which  will  permit 
mechanical  separation  by  coal-washing  or  otherwise.  Lord3 

1  Jour.  Ind.  and  Eng.  Chem.,  1,  307  (1909). 

2  Technical  Paper  171,  Bureau  of  Mines,  1918 

3  Jour.  Ind.  and  Eng.  Chem.,  1,  308  (1909). 


240  GAS  AND  FUEL  ANALYSIS 

recommends  the  use  of  calcium  chloride  solutions  with  which  a 
specific  gravity  as  high  as  1.35  may  be  obtained  or  zinc  chloride 
solutions  with  which  a  specific  gravity  of  2.0  may  be  reached. 
The  coal  is  tested  by  crushing  to  various  degrees  of  fineness  and 
determining  the  differences  in  composition  of  the  portion  which 
floats  and  that  which  sinks  in  solutions  of  varying  specific 
gravities. 

18.  Standard  Methods  for  the  Laboratory  Sampling  and 
Analysis  of  Coal. — In  1899  a  committee  of  the  American  Chemical 
Society1  which  had  made  a  careful  study  of  the  subject  reported 
a  scheme  of  analysis  which  was  very  generally  adopted.  In 
1910  a  joint  committee  of  the  American  Chemical  Society  and 
the  American  Society  for  Testing  Materials  was  appointed  to 
revise  these  methods.  The  committee  made  its  preliminary 
report  in  19132  and  its  final  report  in  1915.  Its  methods  as 
finally  approved  by  the  Society  for  Testing  Materials3  are  given 
below : 

PREPARATION  OF  LABORATORY  SAMPLES 

Apparatus. — Air-drying  Oven. — The  oven  is  to  be  used  for  air-drying 
wet  samples  and  may  be  of  the  form  shown  in  Fig.  50.  This  is  not 
absolutely  necessary  but  is  economical  where  many  wet  samples  are 
received. 

Galvanized-iron  Pans  18  by  18  by  1.5  In.  Deep. — For  air-drying  wet 
samples. 

Balance  or  Solution  Scale. — For  weighing  the  gal\anized-iron  pans 
with  samples.  It  should  have  a  capacity  of  5  kg.  and  be  sensitive  to 
0.5  g. 

Jaw  Crusher. — For  crushing  coarse  samples  to  pass  a  4-mesh  sieve. 

Roll  Crusher  or  Coffee-mill  Typt  of  Grinder. — For  reducing  the  4-mesh 
product  to  20-mesh.  The  coffee-mill  type  of  grinder  should  be  entirely 
enclosed  and  have  an  enclosed  hopper  and  a  receptacle  capable  of  hold- 
ing 10  Ib.  of  coal.  This  is  to  reduce  the  moisture  losses  while  crushing. 

Abbe  Ball  Mill,  Planetary  Disk  Crusher,  Chrome-steel  Bucking  Board, 
or  Any  Satisfactory  Form  of  Pulverizer. — For  reducing  the  20-mesh 
product  to  60-mesh.  The  porcelain  jars  for  the  ball  mill  should  be 
approximately  9  in.  in  diameter  and  10  in,  high.  The  flint  pebbles 
should  be  smooth,  hard  and  well  rounded, 

1  Jour.  Am.  Chem.  Soc.,  21,  1116  (1899). 

2  Jour.  Ind.  and  Eng.  Chem.,  5,  517  (1913), 
*  A.  S.  T.  M.  Standards  for  1918,  p.  679, 


THE  CHEMICAL  ANALYSIS  OF  COAL 


241 


FIG.  50. — Air-drying  oven. 


FIG.  51. — Riffle  sampler. 


16 


242  GAS  AND  FUEL  ANALYSIS 

A  Large  Riffle  Sampler,  with  %  or  %  In.  Divisions. — For  reducing  the 
4-mesh  sample  to  10  Ib.  (Fig.  51). 

A  Small  Riffle  Sampler,  with  %  or  %  In.  Divisions. — For  dividing 
down  the  20  and  60  mesh  material  to  a  laboratory  sample  (Fig.  51). 

An  8-in.  60-mesh  sieve  with  cover  and  receiver. 

Containers  for  Shipment  to  Laboratory. — Samples  in  which  the  mois- 
ture content  is  important  should  always  be  shipped  in  moisture-tight 
containers.  A  galvanized-iron  or  tin  can  with  a  screw  top  which  is 
sealed  with  a  rubber  gasket  and  adhesive  tape  is  best  adapted  to  this 
purpose.  Glass  fruit  jars  sealed  with  rubber  gaskets  may  be  used,  but 
require  very  careful  packing  to  avoid  breakage  in  transit.  Samples  in 
which  the  moisture  content  is  of  no  importance  need  no  special  protec- 
tion from  loss  of  moisture. 

METHOD  OF  SAMPLING 

(A)  When  Coal  Appears  Dry. — If  the  sample  is  coarser  than  4-mesh 
(0.20  in.)  and  larger  in  amount  than  10  Ib.,  quickly  crush  it  with  the 
jaw  crusher  to  pass  a  4-mesh  sieve  and  reduce  it  on  the  larger  riffle 
sampler  to  10  Ib.;  then  crush  at  once  to  20-mesh  by  passing  through 
rolls  or  an  enclosed  grinder,  and  take,  without  sieving,  a  60-g.  total 
moisture  sample,  immediately  after  the  material  has  passed  through 
the  crushing  apparatus.     This  sample  should  be  taken  with  a  spoon 
from  various  parts  of  the  20-mesh  product,  and  should  be  placed  directly 
in  a  rubber-stoppered  bottle. 

Thoroughly  mix  the  main  portion  of  the  sample,  reduce  on  the  small 
riffle  sampler  to  about  120  g.,  and  pulverize  to  60-mesh  by  any  suitable 
apparatus  without  regard  to  loss  of  moisture.  After  all  the  material 
has  been  passed  through  the  60-mesh  sieve,  mix  and  divide  it  on  the 
small  riffle  sampler  to  60  g.  Transfer  the  final  sample  to  a  4-oz.  rubber 
stoppered  bottle.  Determine  moisture  in  both  the  60-  and  20-mesh 
samples  by  the  method  given  under  moisture. 

Computation. — Compute  the  analysis  of  the  60-mesh  coal,  which  has 
become  partly  air-dried  during  sampling,  to  the  dry-coal  basis,  by  divid- 
ing each  result  by  1  minus  its  content  of  moisture.  Compute  the 
analysis  of  the  coal  "as  received"  from  the  dry-coal  analysis  by  multi- 
plying by  1  minus  the  total  moisture  found  in  the  20-mesh  sample. 

(B)  When  Coal  Appears  Wet. — Spread  the  sample  on  tared  pans, 
weigh,  and  air-dry  at  room  temperature,  or  in  the  special  drying  oven, 
shown  in  Fig.  50,  at  10  to  15°  C.  above  room  temperature,  and  weigh 
again.     The  drying  should  be  continued  until  the  loss  in  weight  is  not 
more  than  0.1  per  cent,  per  hour.     Complete  the  sampling  as  under 
dry  coal. 


THE  CHEMICAL  ANALYSIS  OF  COAL  243 

Computation. — Correct  the  moisture  found  in  the  20-mesh  air-dried 
sample  to  total  moisture  "as  received,"  as  follows: 

lOO-percentage  of  air-drying  loss       , 

-  X  (percentage  of  moisture  in  20-mesh 

coal) 
plus   (percentage  of  air-drying  loss)  =  (total  moisture  "as  received") 

Compute  the  analysis  to  "dry-coal"  and  "as  received"  bases  as 
under  dry  coal,  using  for  the  "as  received"  computation  the  total 
moisture  as  found  by  the  formula  in  place  of  the  moisture  found  in 
the  20-mesh  coal. 

Notes. — Freshly  mined  or  wet  coal  loses  moisture  rapidly  on  exposure 
to  the  air  of  the  laboratory,  hence  the  sampling  operations  between  open- 
ing the  container  and  taking  the  20-mesh  total  moisture  sample  must 
be  conducted  with  the  utmost  dispatch  and  with  minimum  exposure 
to  air. 

The  accuracy  of  the  method  of  preparing  laboratory  samples  should 
be  checked  frequently  by  resampling  the  rejected  portions  and  prepar- 
ing a  duplicate  sample.  The  ash  in  the  two  samples  should  not  differ 
more  than  the  following  limits: 

No  carbonates  present 0.4  per  cent. 

Considerable  carbonate  and  pyrite  present 0.7  per  cent. 

Coals  with  more  than  12  per  cent,  ash,  containing 

considerable  carbonate  and  pyrite 1.0  per  cent. 

DETERMINATION  OF  MOISTURE 

Apparatus. — Moisture  Oven. — This  must  be  so  constructed  as  to  have 
a  uniform  temperature  in  all  parts  and  a  minimum  of  air  space.  It 
may  be  of  the  form  shown  in  Fig.  52. 1  Provision  must  be  made  for 
renewing  the  air  in  the  oven  at  the  rate  of  two  to  four  times  a  minute, 
with  the  air  dried  by  passing  it  through  concentrated  H2SO4. 

Capsules  with  Covers. — A  convenient  form,  which  allows  the  ash  de- 
termination to  be  made  on  the  same  sample,  is  the  porcelain  capsule 
No.  2,  %  in.  deep  and  1^  in.  in  diameter;  or  a  fused  silica  capsule  of 
similar  shape.  This  is  to  be  used  with  a  well-fitting  flat  aluminum 
cover,  illustrated  in  Fig.  53. 

Glass  capsules  with  ground-glass  caps  may  also  be  used.  They 
should  be  as  shallow  as  possible,  consistent  with  convenient  handling. 

Method. — (A)  Sixty-mesh  Sample. — Heat  the  empty  capsules  under 
the  conditions  at  which  the  coal  is  to  be  dried,  stopper  or  cover,  cool 
over  concentrated  H2SO4,  sp.  gr.  1.84  for  30  minutes  and  weigh. 

1  Technical  Paper  No.  76,  Bureau  of  Mines. 


244 


GAS  AND  FUEL  ANALYSIS 


FIG.  52. — Moisture  oven  for  coal,  to  contain  toluene  or  glycerine  and  water 


I*"" 
i-  ...  .. 


Dip  out  with  a  spoon  or  spatula  from  the  sample  bottle  approximately 
1  g.  of  coal;  put  this  quickly  into  the  capsule,  close  and  weigh  at  once. 
/3«  An  alternative  procedure  (more  open 

&"  1  to  error),  after  transferring  an  amount 

u*^     •  ^-j  slightly  in  excess  of  1  g.,  is  to  bring  to 

exactly  1  g.  in  weight  (±0.5  mg.)  by 
quickly  removing  the  excess  weight  of 
coal  with  a  spatula.  The  utmost  dis- 
patch must  be  used  in  order  to  minimize 
the  exposure  of  the  coal  until  the  weight 
is  found. 

After  removing  the  covers,  quickly 
place  the  capsules  in  a  pre-heated  oven 
(at  104  to  110°  C.)  through  which  passes 
a  current  of  air  dried  by  concentrated 
H2S04.  Close  the  oven  at  once  and  heat 
for  1  hour.  Then  open  the  oven,  cover 
the  capsules  quickly  and  place  them  in 
a  desiccator  over  concentrated  H2S04.  When  cool,  weigh. 

(B)  Twenty-mesh   Sample. — Use   5-g.   samples,    weighed   with 


FIG.    53. — Porcelain    capsule 
with  flat  aluminium  cover. 


THE  CHEMICAL  ANALYSIS  OF  COAL  245 

accuracy  of  2  mg.,  and  heat  for  1^  hours;  the  procedure  is  otherwise 
the  same  as  with  the  60-mesh  sample.     Methods  of  greater  accuracy 
for  the  determination  of  moisture  are  given  in  the  preliminary  report. 
The  permissible  differences  in  duplicate  determinations  are  as  follows : 

Same  analyst,  Different  analysts, 
per  cent.  per  cent. 

Moisture  under  5  per  cent 0.2  0.3 

Moisture  over  5  per  cent 0.3  0.5 

DETEKMINATION  OF  ASH 

Apparatus. — Gas  or  Electric  Muffle  Furnace. — The  muffle  should  have 
good  air  circulation  and  be  capable  of  having  its  temperature  regulated 
between  700  and  750°  C. 

Porcelain  Capsules. — Porcelain  capsules  No.  2,  %  in.  deep  and  1^  in. 
in  diameter,  or  similar  shallow  dishes. 

Method. — Place  the  porcelain  capsules  containing  the  dried  coal  from 
the  moisture  determination  in  a  cold  muffle  furnace,  or  on  the  hearth 
at  a  low  temperature,  and  gradually  heat  to  redness  at  such  a  rate  as 
to  avoid  mechanical  loss  from  too  rapid  expulsion  of  volatile  matter. 
Finish  the  ignition  to  constant  weight  (  +  0.001  g.)  at  a  temperature 
between  700  and  750°  C.  Cool  in  a  desiccator,  and  weigh  as  soon  as 
cold. 

The  permissible  differences  in  duplicate  determinations  are  as  follows : 

Same  analyst,  Different  analysts, 

per  cent.  per  cent. 

No  carbonates  present 0.2  0.3 

Carbonates  present 0.3  0.5 

Coals  with  more  than  12  per  cent. 
of    ash,    containing    carbonates 

and  pyrite 0.5  1.0 

Notes. — Before  replacing  the  capsules  in  the  muffle  for  ignition  to 
constant  weight,  the  ash  should  be  stirred  with  a  platinum  or  nichrome 
wire.  Stirring  once  or  twice  before  the  first  weighing  hastens  complete 
ignition. 

The  result  obtained  by  this  method  is  "unconnected"  ash.  For 
"corrected"  ash  see  the  preliminary  report  as  quoted  on  p.  230.  The 
actual  mineral  matters  in  the  original  coal  are  usually  very  different  in 
weight  and  composition  from  the  weight  of  the  "  uncorrected "  ash. 

DETERMINATION  OF  VOLATILE  MATTER 

Apparatus. — Platinum  Crucible  with  Tightly  Fitting  Cover. — The  cruci- 
ble should  be  of  not  less  than  10  nor  more  than  20-c,c,  capacity;  of 


246 


GAS  AND  FUEL  ANALYSIS 


not  less  than  25  nor  more  than  35  mm.  in  diameter;  of  not  less  than  30 
nor  more  than  35  mm.  in  height. 

Vertical  Electric  Tube  Furnace;  or  a  Gas  or  Electrically  Heated  Muffle 
Furnace. — The  furnace  may  be  of  the  form  as  shown  in  Fig.  54.     It  is 


Platinum  rhodium-  •' 
FIG.  54. — Electric  tube  furnace  for  determining  volatile  matter  in  coal. 

to  be  regulated  to  maintain  a  temperature  of  950°  C.(±20°  C.)  in  the 
crucible,  as  shown  by  a  thermocouple  kept  in  the  furnace.  A  suitable 
form  of  electric  furnace  is  shown  in  Fig.  54.  If  the  determination  of 
volatile  matter  is  not  an  essential  feature  of  the  specifications  under 
which  the  coal  is  bought,  a  Meker  burner  may  be  used. 


THE  CHEMICAL  ANALYSIS  OF  COAL  247 

Method. — Weigh  1  g.  of  the  coal  in  a  weighed  10  to  20-c.c.  platinum 
crucible,  close  with  a  capsule  cover,  and  place  on  platinum  or  nichrome- 
wire  supports  in  the  furnace  chamber,  which  must  be  at  a  temperature 
of  950°  C.  (±20°  C.).  After  the  more  rapid  discharge  of  volatile  mat- 
ter has  subsided,  as  shown  by  the  disappearance  of  the  luminous  flame, 
tap  the  cover  lightly  to  more  perfectly  seal  the  crucible  and  thus  guard 
against  the  admission  of  air.  After  heating  exactly  7  minutes,  remove 
the  crucible  from  the  furnace  and,  without  disturbing  the  cover,  allow 
it  to  cool.  Weigh  as  soon  as  cold.  The  loss  of  weight  minus  moisture 
equals  the  volatile  matter. 

Modification  for  Sub-bituminous  Coal,  Lignite,  and  Peat. — Mechanical 
losses  are  incurred  on  suddenly  heating  peat,  sub-bituminous  coal,  and 
lignite;  therefore  they  must  be  subjected  to  a  preliminary  gradual  heat- 
ing for  5  minutes;  this  is  best  done  by  playing  the  flame  of  a  burner 
upon  the  bottom  of  the  crucible  in  such  a  manner  as  to  bring  about 
the  discharge  of  volatile  matter  at  a  rate  not  sufficient  to  cause  sparking. 
After  the  preliminary  heating,  transfer  the  crucible  to  the  volatile-matter 
furnace  and  heat  for  6  minutes  at  950°  C.  as  in  the  regular  method. 

The  permissible  differences  in  duplicate  determinations  are  as  follows : 


Same  analyst,  Different  analysts, 
per  cent.  per  cent. 

Bituminous  coals 0.5  1.0 

Lignites 1.0  2.0 


Notes.— The  cover  should  fit  closely  enough  so  that  the  carbon 
deposit  from  bituminous  and  lignite  coals  does  not  burn  away  from  the 
under  side. 

Regulation  of  temperature  to  within  the  prescribed  limits  is  important. 

DETERMINATION  OF  FIXED  CARBON 

Compute  fixed  carbon  as  follows: 

100  —  (moisture  plus  ash  plus  volatile  matter)  equals  percentage  of 
fixed  carbon. 

DETERMINATION  OF  SULPHUR  BY  THE  ESCHKA  METHOD 

Apparatus. — Gas  or  Electric  Muffle  Furnace,  or  Burners. — For  igniting 
coal  with  the  Eschka  mixture  and  for  igniting  the  BaS04. 

Porcelain,  Silica,  or  Platinum  Crucibles  or  Capsules. — For  igniting  coal 
with  the  Eschka  mixture. 

No.  1  porcelain  capsule,  1  in.  deep  and  2  in.  in  diameter.  This 
capsule,  because  of  its  shallow  form,  presents  more  surface  for 


248  GAS  AND  FUEL  ANALYSIS 

oxidation  and  is  more  convenient  to  handle  than  the  ordinary  form 
of  crucible. 

No.  1  porcelain  crucibles,  shallow  form,  and  platinum  crucibles  of 
similar  size  may  be  used.  Somewhat  more  time  is  required  to  burn 
out  the  coal,  owing  to  the  deeper  form,  than  with  the  shallow  capsules 
described  above. 

No.  0  or  00  porcelain  crucibles,  or  platinum,  alundum  or  silica  cru- 
cibles of  similar  size  are  to  be  used  for  igniting  the  BaSC>4. 

Solutions  and  Reagents. — Barium  Chloride. — Dissolve  100  g.  of 
BaCl2.2H20  in  1000  c.c.  of  distilled  water. 

Saturated  Bromine  Water. — Add  an  excess  of  bromine  to  1000  c.c.  of 
distilled  water. 

Eschka  Mixture. — Thoroughly  mix  2  parts  (by  weight)  of  light  cal- 
cined MgO  and  1  part  of  anhydrous  Na2COa.  Both  materials  should 
be  as  free  as  possible  from  sulphur. 

Methyl  Orange. — Dissolve  0.02  g.  in  100  c.c.  of  hot  distilled  water 
and  filter. 

Hydrochloric  Acid. — Mix  500  c.c.  of  HC1,  sp.  gr.  1.20,  and  500  c.c.  of 
distilled  water. 

Normal  Hydrochloric  Acid. — Dilute  80  c.c.  of  HC1,  sp.  gr.  1.20,  to  1 
liter  with  distilled  water. 

Sodium  Carbonate. — A  saturated  solution,  approximately  60  g.  of 
crystallized  or  22  g.  of  anhydrous  Na2COa  in  100  c.c.  of  distilled  water. 

Sodium-hydroxide  Solution. — Dissolve  100  g.  in  1  liter  of  distilled 
water.  This  solution  may  be  used  in  place  of  the  Na2COs  solution. 

Method. — Preparation  of  Sample  and  Mixture. — Thoroughly  mix  on 
glazed  paper  1  g.  of  coal  and  3  g.  of  Eschka  mixture.  Transfer  to  a 
No.  1  porcelain  capsule,  1  in.  deep  and  2  in.  in  diameter,  or  a  No.  1 
crucible  or  a  platinum  crucible  of  similar  size,  and  cover  with  about 
1  g.  of  Eschka  mixture. 

Ignition. — On  account  of  the  amount  of  sulphur  contained  in  artificial 
gas,  the  crucible  shall  be  heated  over  an  alcohol,  gasoline  or  natural 
gas  flame  as  in  procedure  (a)  below,  or  in  a  gas  or  electrically  heated 
muffle,  as  in  procedure  (b)  below.  The  use  of  artificial  gas  for  heating 
the  coal  and  Eschka  mixture  is  permissible  only  when  the  crucibles 
are  heated  in  a  muffle. 

(a)  Heat  the  crucible,  placed  in  a  slanting  position  on  a  triangle, 
over  a  very  low  flame  to  avoid  rapid  expulsion  of  the  volatile  matter, 
which  tends  to  prevent  complete  absorption  of  the  products  of  com- 
bustion of  sulphur.  Heat  the  crucible  slowly  for  30  minutes,  gradually 
increasing  the  temperature  and  stirring  after  all  black  particles  have 
disappeared,  which  is  an  indication  of  the  completeness  of  the  procedure. 


THE  CHEMICAL  ANALYSIS  OF  COAL  249 

(6)  Place  the  crucible  in  a  cold  muffle  and  gradually  raise  the  tem- 
perature to  870-925°  C.  (cherry-red  heat)  in  about  1  hour.  Maintain 
the  maximum  temperature  for  about  \%  hours  and  then  allow  the 
crucible  to  cool  in  the  muffle. 

Subsequent  Treatment. — Remove  and  empty  the  contents  into  a  200- 
c.c.  beaker  and  digest  with  100  c.c.  of  hot  water  for  H  to  %  hour,  with 
occasional  stirring.  Filter  and  wash  the  insoluble  matter  by  decanta- 
tion.  After  several  washings  in  this  manner,  transfer  the  insoluble 
matter  to  the  filter  and  wash  5  times,  keeping  the  mixture  well  agitated. 
Treat  the  filtrate  amounting  to  about  250  c.c.,  with  10  to  20  c.c.  of  satu- 
rated bromine  water,  make  slightly  acid  with  HC1  and  boil  to  expel 
the  liberated  bromine.  Make  just  neutral  to  methyl  orange  with  NaOH 
or  Na2CO3  solution,  then  add  1  c.c.  of  normal  HC1.  Boil  again  and 
add  slowly  from  a  pipette,  with  constant  stirring,  10  c.c.  of  a  10  per 
cent,  solution  of  BaCl2.2H20.  Continue  boiling  for  15  minutes  and 
allow  to  stand  for  at  least  2  hours,  or  preferably  over  night,  at  a  tem- 
perature just  below  boiling.  Filter  through  an  ashless  filter  paper  and 
wash  with  hot  distilled  water  until  a  AgN03  solution  shows  no  precipi- 
tate with  a  drop  of  the  filtrate.  Place  the  wet  filter  containing  the 
precipitate  of  BaSC>4  in  a  weighed  platinum,  porcelain,  silica  or  alundum 
crucible,  allowing  a  free  access  of  air  by  folding  the  paper  over  the  pre- 
cipitate loosely  to  prevent  spattering.  Smoke  the  paper  off  gradually 
and  at  no  time  allow  it  to  burn  with  a  flame.  After  the  paper  is  prac- 
tically consumed,  raise  the  temperature  to  approximately  925°  C.  and 
heat  to  constant  weight. 

The  residue  of  MgO,  etc.,  after  leaching,  should  be  dissolved  in  HC1 
and  tested  with  great  care  for  sulphur.  When  an  appreciable  amount 
is  found  this  should  be  determined  quantitatively.  The  amount  of 
sulphur  retained  is  by  no  means  a  negligible  quantity. 

Blanks  and  Corrections. — In  all  cases  a  correction  must  be  applied 
either  (1)  by  running  a  blank  exactly  as  described  above,  using  the 
same  amount  of  all  reagents  that  were  employed  in  the  regular  deter- 
mination, or  more  surely  (2)  by  determining  a  known  amount  of  sul- 
phate added  to  a  solution  of  the  reagents  after  these  have  been  put 
through  the  prescribed  series  of  operations.  If  this  latter  procedure  is 
adopted  and  carried  out,  say,  once  a  week  or  whenever  a  new  supply 
of  a  reagent  must  be  used,  and  for  a  series  of  solutions  covering  the  range 
of  sulphur  content  likely  to  be  met  with  in  coals,  it  is  only  necessary 
to  add  to  or  subtract  deficiency  or  excess  may  have  been  found  in  the 
appropriate  "check"  in  order  to  obtain  a  result  that  is  more  certain 
to  be  correct  than  if  a  " blank"  correction  as  determined  by  the  former 
procedure  is  applied.  This  is  due  to  the  fact  that  the  solubility  error 


250  GAS  AND  FUEL  ANALYSIS 

for  BaSCh,  for  the  amounts  of  sulphur  in  question  and  the  conditions 
of  precipitation  prescribed,  is  probably  the  largest  one  to  be  considered. 
BaS(>4  is  soluble  in  acids  and  even  in  pure  water,  and  the  solubility 
limit  is  reached  almost  immediately  on  contact  with  the  solvent. 
Hence,  in  the  event  of  using  reagents  of  very  superior  quality  or  of 
exercising  more  than  ordinary  precautions,  there  may  be  no  apparent 
"blank,"  because  the  solubility  limit  of  the  solution  for  BaS04  has  not 
been  reached  or  at  any  rate  not  exceeded. 

As  shown  in  the  preliminary  report,  the  Atkinson  and  sodium- 
peroxide  methods  give  results  in  close  agreement  with  theEschka 
method.  Regester  has  shown  that  if  5  per  cent,  of  nitrogen  is  present 
in  the  gases  contained  in  the  bomb  calorimeter  the  sulphur  of  a  coal  is 
almost  completely  oxidized  to  H2S04  and  the  washings  of  the  calori- 
meter may  be  used  for  the  determination  of  sulphur. 

The  permissible  differences  in  duplicate  determinations  are  as  follows: 

Same  analyst,  Different  analysts, 
per  cent.  per  cent. 

Sulphur  under  2  per  cent 0 . 05  0.10 

Sulphur  over  2  per  cent 0. 10  0. 20 

DETERMINATION  OF  PHOSPHORUS  IN  ASH 

Method  No.  1.  To  Cover  All  Cases. — To  the  ash  from  5  g.  of  coal 
in  a  platinum  capsule  is  added  10  c.c.  of  HN03  and  3  to  5  c.c.  of  HF. 
The  liquid  is  evaporated  and  the  residue  fused  with  3  g.  of  Na2C03.  If 
unburned  carbon  is  present  0.2  g.  of  NaN03  is  mixed  with  carbonate. 
The  melt  is  leached  with  water  and  the  solution  filtered.  The  residue 
is  ignited,  fused  with  Na2C03  alone,  the  melt  leached  and  the  solution 
filtered.  The  combined  filtrates,  held  in  a  flask,  are  just  acidified  with 
HN03  and  concentrated  to  a  volume  of  100  c.c.  To  the  solution, 
brought  to  a  temperature  of  85°  C.,  is  added  50  c.c.  of  molybdate 
solution  and  the  flask  is  shaken  for  10  minutes.  If  the  precipitate 
does  not  form  promptly  and  subside  rapidly,  add  enough  NH4N03  to 
cause  it  to  do  so.  The  precipitate  is  washed  six  times,  or  until  free 
from  acid,  with  a  2-per-cent.  solution  of  KN03,  then  returned  to  the 
flask  and  titrated  with  standard  NaOH  solution.  The  alkali  solution 
may  well  be  made  equal  to  0.00025  g.  phosphorus  per  cubic  centimeter, 
or  0.005  per  cent,  for  a  5-g.  sample  of  coal,  and  is  0.995  of  one-fifth 
normal.  Or  the  phosphorus  in  the  precipitate  is  determined  by  reduc- 
tion and  titration  of  the  molybdenum  with  permanganate. 

Note  on  Method  1. — The  advantage  of  the  use  of  HF  in  the  initial 
attack  of  the  ash  lies  in  the  resulting  removal  of  silica.  Fusion  with 


THE  CHEMICAL  ANALYSIS  OF  COAL  251 

alkali  carbonate  is  necessary  for  the  elimination  of  titanium,  which  if 
present  and  not  removed  will  contaminate  the  phospho-molybdate  and 
is  said  to  sometimes  retard  its  precipitation. 

Method  No.  2. — When  titanium  is  so  low  as  to  offer  no  objection, 
the  ash  is  decomposed  as  under  method  No.  1,  but  evaporation  is  carried 
only  to  a  volume  of  about  5  c.c.  The  solution  is  diluted  with  water  to 
30  c.c.,  boiled  and  filtered.  If  the  washings  are  turbid  they  are  passed 
again  through  the  filter.  The  residue  is  ignited  in  a  platinum  crucible 
fused  with  a  little  NaaCOs,  the  melt  dissolved  in  HNOs  and  its  solution, 
if  clear,  added  to  the  main  one.  If  not  clear  it  is  filtered.  The  sub- 
sequent procedure  is  as  under  method  No.  1.  The  fusion  of  the  residue 
may  be  dispensed  with  in  routine  work  on  a  given  coal  if  it  is  certain 
that  it  is  free  from  phosphorus. 

ULTIMATE  ANALYSIS 

Carbon  and  Hydrogen. — The  determination  of  carbon  and  of  hydro- 
gen is  made  with  a  weighed  quantity  of  sample  in  a  25-burner  combus- 
tion furnace  of  the  Glaser  type.  The  products  of  combustion  are 
thoroughly  oxidized  by  being  passed  over  red-hot  CuO  and  PbCrO4, 
and  are  fixed  by  absorbing  the  water  in  a  weighed  Marchand  tube  filled 
with  granular  CaCls  and  by  absorbing  the  CO2  in  a  Liebig  bulb  con- 
taining a  30  per  cent,  solution  of  KOH. 

The  apparatus  used  consists  of  a  purifying  train,  in  duplicate,  a 
combustion  tube  in  the  furnace,  and  an  absorption  train.  The  puri- 
fying train  consists  of  the  following  purifying  reagents  arranged  in 
order  of  passage  of  air  and  oxygen  through  them:  H2SO4,  KOH  solu- 
tion, soda  lime,  and  granular  CaCl?.  One  of  the  trains  is  for  air  and 
one  for  oxygen.  In  the  H2S04  and  KOH  scrubbing  bottles  the  air  and 
the  oxygen  are  made  to  bubble  through  about  5  mm.  of  the  purifying 
reagent.  Both  purifying  trains  are  connected  to  the  combustion  tube 
by  a  Y-tube,  the  joint  being  made  tight  by  a  rubber  stopper. 

The  combustion  tube  is  made  of  hard  Jena  glass.  Its  external  diam- 
eter is  about  21  mm.,  and  its  total  length  is  1  meter.  The  first  30  cm. 
of  the  tube  are  empty;  following  this  empty  space  is  an  asbestos  plug 
(acid-washed  and  ignited),  or  in  its  place  a  roll  of  oxidized  copper  gauze 
may  be  used;  the  next  40  cm.  are  filled  with  "wire"  CuO;  a  second 
asbestos  plug  separates  the  copper  oxide  from  10  cm.  of  fused  PbCrO4, 
which  is  held  in  place  by  another  asbestos  plug  20  cm.  from  the  end  of 
the  tube.  The  end  of  the  tube  is  drawn  out  for  rubber-tubing  connec- 
tion with  the  absorption  train. 

The  absorption  train  consists,  first,  of  a  Marchand  tube  filled  with 
granular  CaCl2  to  absorb  moisture.  The  CaClj  should  be  saturated 


252  GAS  AND  FUEL   ANALYSIS 

\vith  CO2  before  using.  The  Marchand  tube  is  followed  by  a  Liebig 
bulb  containing  a  30  per  cent.  KOH  solution,  in  which  any  possible 
impurities,  as  ferrous  iron  or  nitrites,  have  been  oxidized  by  a  little 
KMnC>4.  A  guard  tube  containing  granular  CaCl2  and  soda  lime,  is 
attached  to  the  Liebig  bulb  to  absorb  any  CO2  escaping  the  KOH 
solution  and  any  water  evaporating  from  that  solution. 

The  train  is  connected  to  an  aspirator  which  draws  the  products  of 
combustion  through  the  entire  train.  A  guard  tube  of  CaCl2  prevents 
moisture  from  running  back  into  the  absorption  train.  The  suction  is 
maintained  constant  by  a  Mariotte  flask.  The  advantage  of  aspirating 
the  gases  through  the  train  rather  than  forcing  them  through  by  pres- 
sure is  that  the  pressure  on  the  rubber  connections  is  from  the  outside, 
so  that  gas-tight  connections  are  more  easily  maintained  than  if  the 
pressure  is  on  the  inside  of  the  tube.  The  connections  are  made  as 
tight  as  possible.  The  usual  test  for  tightness  is  to  start  aspiartion 
at  the  rate  of  about  three  bubbles  of  air  per  second  through  the  potash 
bulb,  and  then  to  close  the  inlet  for  air  and  oxygen  at  the  opposite  end 
of  the  train;  if  there  is  no  more  than  one  bubble  per  minute  in  the 
potash  bulb,  the  apparatus  is  considered  tight. 

Before  starting  a  determination  when  the  train  has  been  idle  some 
hours,  or  after  any  changes  in  chemicals  or  connections,  a  blank  is  run 
by  aspirating  about  1  liter  of  air  through  the  train  which  is  heated  in 
the  same  manner  as  if  a  determination  on  coal  were  being  made.  If  the 
Liebig  bulb  and  the  tube  containing  calcium  chloride  show  a  change  in 
weight  of  less  than  0.5  mg.  each,  the  apparatus  is  in  proper  condition 
for  use. 

A  porcelain  or  platinum  boat  is  provided  with  a  glass  weighing  tube 
of  suitable  size,  which  is  fitted  with  an  accurately  ground  glass  stopper. 
The  tube  and  empty  boat  are  weighed.  Approximately  0.2  g.  of  the 
air-dry  coal  (60-mesh  and  finer,  or  better  100-mesh  if  much  free  im- 
purity is  present)  are  quickly  placed  in  the  boat.  The  boat  is  at  once 
placed  in  the  weighing  tube,  which  is  quickly  stoppered  to  prevent 
moisture  change  in  the  coal  while  weighing,  and  transferring  to  the 
furnace.  The  absorption  tubes  are  connected  and  the  boat  and  sample 
are  transferred  from  the  weighing  tube  to  the  combustion  tube,  which 
should  be  cool  for  the  first  30  cm.  The  CuO  should  be  red  hot  and  the 
PbCrO4  at  a  dull-red  heat.  The  transfer  of  the  boat  from  weighing 
tube  to  combustion  tube  should  be  made  as  rapidly  as  possible.  As 
soon  as  the  boat  is  in  place  near  the  asbestos  plug  at  the  beginning  of 
the  copper  oxide  the  stopper  connecting  with  the  purifying  train  is 
inserted  and  the  aspiration  started  with  pure  oxygen  gas  at  the  rate  of 
three  bubbles  per  second.  One  burner  is  turned  on  about  10  cm.  back 


THE  CHEMICAL  ANALYSIS  OF  COAL  253 

from  the  boat,  and  the  aspiration  is  continued  carefully  until  practi- 
cally all  the  moisture  is  expelled  from  the  sample.  The  heat  is  then 
increased  very  gradually  until  all  the  volatile  matter  has  been  driven 
off.  In  driving  off  the  volatile  matter  the  heat  must  be  applied  gradu- 
ally in  order  to  prevent  a  too  rapid  evolution  of  gas  and  tar,  which  may 
either  escape  complete  combustion  or  may  be  driven  back  into  the  puri- 
fying train.  The  heat  should  be  slowly  increased  by  turning  on  more 
burners  under  the  open  part  of  the  tube  until  the  sample  is  ignited; 
then  the  temperature  can  be  increased  rapidly,  but  care  should  be  taken 
not  to  melt  the  combustion  tube.  Any  moisture  collecting  in  the  end 
of  the  combustion  tube  or  in  the  rubber  connection  joining  it  to  the 
CaCl2  tube  is  driven  over  into  the  CaCl2  tube  by  carefully  warming 
with  a  piece  of  hot  tile.  The  aspiration  with  oxygen  is  continued  for 
2  minutes  after  the  sample  ceases  to  glow,  the  heat  is  then  turned  off 
and  about  1200  c.c.  of  air  are  aspirated.  The  absorption  bulbs  are 
then  disconnected,  wiped  with  a  clean  cloth,  and  allowed  to  cool  to  the 
balance-room  temperature  before  weighing. 

11.19  X  (increase  in  weight  of  CaCl2  tube) 
Percentage  of  hydrogen  =  Weight  of  sample 

27.27  X  (increase  in  weight  of  KOH  bulb) 

Percentage  of  carbon  = ~7  .  ,       , 

Weight  of  sample 

The  ash  in  the  boat  is  weighed  and  carefully  inspected  for  any  un- 
burned  carbon,  which  would  destroy  the  value  of  the  determination. 

Method  with  Electrically  Heated  Combustion  Furnace. — An  electrically 
heated  combustion  furnace  of  the  Heraeus  type  is  used  by  the  Bureau 
of  mines.  It  consists  of  three  independent  heaters,  two  of  which  are 
provided  with  sheave  wheels,  and  are  mounted  on  a  track  so  that  they 
are  movable  along  the  tube;  the  third  heater  which  surrounds  the 
PbCr04,  is  stationary.  The  furnace  as  provided  by  the  manufacturer 
does  not  include  the  small  stationary  heater.  This  can  be  made  in  the 
laboratory  by  winding  an  alundum  tube  12  cm.  in  length  with  No.  20 
nichrome  II  wire  and  enclosing  it  in  a  cylinder  packed  with  magnesia 
asbestos.  The  movable  heaters  have  very  thin  platinum  foil,  weighing 
about  9  g.  in  all,  wound  on  a  porcelain  tube  of  30  mm.  internal  diam- 
eter. The  larger  one  which  heats  the  CuO,  is  350  mm.  in  length,  and 
the  smaller  one,  which  heats  the  sample  in  the  boat,  is  200  mm.  in 
length.  The  Jena  glass  or  fused  silica  combustion  tube,  about  21 
mm.  external  diameter  and  900  mm.  in  length,  is  supported  by  an  asbes- 
tos-lined nickel  trough.  The  current  through  each  heater  is  regulated 
independently  by  separate  rheostats,  mounted  on  the  frame  of  the 
furnace.  The  two  platinum-wound  heaters  require  an  average  current 


254  GAS  AND  FUEL  ANALYSIS 

of  about  4.5  amperes  at  a  pressure  of  220  volts,  although  for  heating 
rapidly  a  larger  amperage  is  necessary. 

The  oxygen  or  air  entering  the  combustion  tube  is  purified  by 
passing  through  a  Tauber's  drying  apparatus,  which  contains  the 
following  reagents  arranged  in  order  of  the  passage  of  air  or  oxygen 
through  them:  H2S04,  for  removing  posible  traces  of  ammonia,  30 
per  cent.  KOH  solution,  granular  soda  lime,  and  granular  CaCl2.  One 
side  of  the  train  is  connected  directly  to  a  Linde  oxygen  tank,  which  is 
provided  with  a  reducing  valve  for  regulating  the  oxygen  pressure ;  the 
other  side  of  the  train  is  used  for  purifying  the  air  supply. 

The  absorption  train  consists  of  a  5-in.  U-tube,  filled  with  granular 
CaCl2  to  absorb  moisture.  Before  using,  the  CaCl2  should  be  saturated 
with  C02  to  avoid  possible  absorption  of  C02  during  a  determination 
by  any  traces  of  CaO  that  may  be  present.  This  saturating  is  done 
most  conveniently  by  placing  a  quantity  of  CaCl2  in  a  large  drying 
jar,  and%  filling  the  jar  with  C02.  After  standing  over  night,  dry  air  is 
drawn  through  the  jar  to  remove  the  CO2.  The  treated  CaCl2  is  kept 
in  well-stoppered  bottles. 

The  CaCl2  tube  is  connected  to  a  Vanier  potash  bulb  containing  a 
30  per  cent.  KOH  solution  and  granular  CaCl2.  Six  to  eight  determin- 
ations can  be  made  without  recharging  this  bulb.  The  potash  bulb  is 
connected  to  an  aspirator  through  a  guard  tube  containing  granular 
CaCl2  and  soda  lime,  and  a  guard  tube  containing  granular  CaCl2  and 
soda  lime  and  a  Mariotte  flask.  The  Mariotte  flask  keeps  the  pressure 
constant. 

In  general,  the  method  of  determination  is  the  same  as  the  one  used 
with  the  gas  furnace.  By  moving  the  heaters  toward  the  end  of  the 
tube  where  the  gases  enter,  and  cutting  in  the  electric  current,  the  air 
can  be  warmed  enough  to  thoroughly  dry  the  tube  and  its  contents. 
The  current  is  then  cut  off  from  the  small  heater  ,and  the  large  heater 
is  moved  over  the  CuO;  about  250  mm.  of  that  part  of  the  combustion 
tube  between  the  two  heaters  where  the  boat  containing  the  sample 
to  be  placed  is  kept  exposed.  The  full  current  is  then  turned  on  the 
large  heater  to  bring  the  CuO  to  a  red  heat.  When  this  temperature 
is  reached  it  is  necessary  to  reduce  the  current  with  the  rheostat  to 
avoid  melting  the  tube.  In  the  meantime  the  absorption  train  is 
weighed  and  connected,  and  the  boat  containing  the  sample  is  placed 
in  the  exposed  and  cooler  part  of  the  tube  between  the  two  heaters. 

The  current  is  then  passed  through  the  shorter  heater.  By  manipu- 
lating the  rheostat  and  by  gradually  pushing  this  heater  toward  the 
boat,  the  rate  of  evaporation  of  moisture  and  evolution  of  volatile 
matter  can  be  readily  controlled. 


THE  CHEMICAL  ANALYSIS  OF  COAL  255 

After  combustion  is  complete,  the  electric  current  is  turned  off  the 
smaller  heater  and  this  heater  moved  back  to  allow  the  tube  to  cool  for 
the  next  determination.  The  final  aspiration  of  air  and  the  weighing 
of  the  absorption  train  is  conducted  as  described  under  the  gas-furnace 
method. 

Note. — In  place  of  granulated  CaCl2,  concentrated  H2S04,  may  be 
used  for  collecting  the  water  formed  by  combustion.  In  such  cases 
the  air  and  oxygen  entering  the  combustion  tube  and  the  gas  leaving 
the  potash  bulb  must  also  be  dried  by  H2S04. 

Other  suitable  forms  of  absorption  vessels  than  those  indicated  in 
the  above  procedure  may  be  used. 

NITROGEN 

The  Kjeldahl-Gunning  method  is  recommended  for  the  determination 
of  nitrogen  This  method  has  the  advantage  over  either  the  simple 
Kjeldahl  or  the  Gunning  method,  in  requiring  less  time  for  the  complete 
oxidation  of  the  organic  matter,  and  in  giving  the  most  uniform  results. 

The  Kjeldahl-Gunning  Method. — One  gram  of  the  coal  sample  is  boiled 
with  30  c.c.  of  concentrated  H2S04,  7  to  10  g.  of  K2S04,  and  0.6  to  0.8  g. 
of  metallic  mercury  in  a  500  c.c.  Kjeldahl  flask  until  all  particles  of  coal 
are  oxidized  and  the  solution  nearly  colorless.  The  boiling  should  be 
continued  at  least  2  hours  after  the  solution  has  reached  the  straw- 
colored  stage.  The  total  time  of  digestion  will  be  from  3  to  4  hours. 
The  addition  of  a  few  crystals  of  KMn04  after  the  solution  has  cooled 
enough  to  avoid  violent  reaction,  tends  to  insure  complete  oxidation. 

After  cooling,  the  solution  is  diluted  to  about  200  c.c.  with  cold  water. 
If  the  dilution  with  water  has  warmed  the  solution,  it  should  be  cooled 
again  and  the  following  reagents  added:  25  c.c.  K2S  solution  (40  g. 
K2S  per  liter)  to  precipitate  the  mercury;  1  to  2  g.  of  granular  zinc  to 
prevent  bumping;  and  finally  enough  strong  NaOH  solution  (usually 
80  to  100  c.c.)  to  make  the  solution  distinctly  alkaline.  The  danger 
of  loss  of  NH3  may  be  minimized  by  holding  the  flask  in  an  inclined 
position  while  the  NaOH  solution  is  being  added.  The  alkaline  solu- 
tion runs  down  the  side  of  the  flask  in  an  inclined  position  while  the 
NaOH  solution  is  being  added.  The  alkaline  solution  runs  down  the 
side  of  the  flask  and  forms  a  layer  below  the  lighter  acid  solution. 
After  adding  the  alkaline  solution,  the  flask  is  at  once  connected  to  the 
condensing  apparatus  and  the  solution  mixed  by  gently  shaking  the 
flask. 

The  NH3  is  distilled  over  into  a  measured  amount  (10  c.c.)  of  stand- 
ard H2S04  solution,  to  which  has  been  added  sufficient  cochineal  indi- 
cator for  titration.  Care  should  be  taken  that  the  glass  connecting 
tube  on  the  end  of  the  condenser  dips  under  the  surface  of  the  standard 


256  GAS  AND  FUEL  ANALYSIS 

acid.  The  solution  is  slowly  distilled  until  150  to  200  c.c.  of  distillate 
has  passed  over.  To  avoid  mechanically  entrained  alkali  passing  over 
into  the  condenser,  the  rate  of  distillation  should  not  exceed  100  c.c. 
per  hour.  The  distillate  is  titrated  with  standard  NH3  solution  (20  c.c. 
NH4OH  solution  =  10  c.c.  H2S04  solution  =  0.05  g.  nitrogen).  Stand- 
ard NaOH  or  KOH  solution  with  methyl  orange  or  methyl  red  as  indi- 
cator may  be  used  instead  of  NH3  and  cochineal. 

A  blank  determination  should  be  made  in  exactly  the  same  manner 
as  described  above,  except  that  1  g.  of  pure  sucrose  (cane  sugar)  is 
substituted  in  place  of  the  coal  sample.  The  nitrogen  found  in  this 
blank  determination  is  deducted  from  the  result  obtained  with  the  coal 
sample. 

The  K2S  and  NaOH  may  be  dissolved  in  a  single  stock  solution. 
Sufficient  K2S  is  dissolved  in  the  water  before  adding  the  NaOH  to 
make  a  solution  in  which  the  quantity  necessary  for  a  nitrogen  deter- 
mination (80  to  100  c.c.)  contains  1  g.  of  K2S.  Twelve  grams  of  K2S 
and  500  g.  of  NaOH  in  one  liter  of  water  are  required  for  the  above 
proportions. 

Coke  and  anthracite  should  be  ground  to  an  impalpable  powder  as 
they  are  very  difficult  to  oxidize.  Even  if  this  is  done  the  digestion 
may  require  12  to  16  hours. 

OXYGEN 

There  being  no  satisfactory  direct  method  of  determining  oxygen, 
it  is  computed  by  subtracting  the  sum  of  the  percentages  of  hydrogen, 
carbon,  nitrogen,  sulphur,  water  and  ash  from  100.  The  result  so  ob- 
tained is  affected  by  all  the  errors  incurred  in  the  other  determinations 
and  especially  by  the  change  in  weight  of  the  ash-forming  constituents 
on  ignition;  iron  pyrite  changes  to  ferric  oxide,  increasing  the  ash  and 
causing  a  negative  error  in  the  oxygen  equivalent  to  three-eighths  of 
the  pyritic  sulphur.  On  the  other  hand,  there  is  always  a  loss  on  igni- 
tion, of  water  of  composition  from  the  clayey  and  shaley  constituents, 
C02  from  carbonates,  etc.,  which  tends  to  compensate  the  absorption 
of  oxygen. 

Corrected  Oxygen. — When  a  more  correct  oxygen  value  is  desired,  it 
may  be  obtained  by  making  the  corrections  indicated  in  the  following 
formula: 

Corrected  oxygen  =  100  -  [(C  -  C')  plus  (H  -  H')  plus  N  plus 

H20  plus  S'  plus  corrected  ash.] 
in  which 

C  equals  total  carbon 

C'  equals  carbon  of  carbonates 


THE  CHEMICAL  ANALYSIS  OF  COAL  257 

H  equals  total  hydrogen  less  hydrogen  of  water 
H'  equals  hydrogen  from  water  of  composition  in  clay,  shale,  etc. 
N  equals  nitrogen 

HaO  equals  moisture  as  found  at  105°  C. 

S'  equals  sulphur  not  present  as  pyrite  or  sulphate.     This  is  usually 
small.     In  many  types  of  coal  it  may  be  disregarded. 

CORRECTED  ASH 

Corrected  ash  equals  mineral  constituents  originally  present  in  the 
coal.  For  most  purposes  this  can  be  determined  with  sufficient  accur- 
acy by  adding  to  the  ash,  as  found,  five-eighths  of  the  weight  of  pyritic 
sulphur,  the  CO2  of  carbonates  and  the  water  of  composition  of  clay, 
shale,  etc.  See  also  Determination  of  Ash. 

19.  Standard  Methods  for  Laboratory  Sampling  and  Analysis 
of  Coke.1 — The  American  Society  for  Testing  Materials  has 
issued  a  standard  method  for  sampling  and  analysis  of  coke 
which  in  general  follows  the  lines  laid  down  for  coal.  Coke  is 
so  very  abrasive  that  especial  care  must  be  taken  not  to  in- 
crease the  ash  of  the  sample  during  crushing.  The  samples 
may  be  coarsely  crushed  with  a  jaw  or  roll  crusher  or  by  hand 
on  a  chilled  iron  or  hard-steel  plate  by  impact  of  a  hard  bar  or 
sledge,  avoiding  all  rubbing  action.  The  use  of  rubbing  sur- 
faces such  as  a  disk  pulverizer  or  a  bucking  board  is  never  per- 
missible for  grinding  coke.  The  final  grinding  to  60  mesh  may 
be  made  in  a  porcelain  jar  mill.  No  special  care  is  needed  in 
determining  moisture  which  may  be  done  in  an  ordinary  oven 
at  104-110°  C.  The  other  methods  follow  those  for  coal  quite 
closely. 

The  American  Society  for  Testing  Materials  Standards  1918,  p.  709. 


17 


CHAPTER  XVI 
HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER 

1,  General  Methods  of  Determining    Heating  Value. — The 
heating  value  of  a  fuel  is  determined  either  directly  in  a  calori- 
meter or  indirectly  by  calculation  from  its  chemical  composition. 
The  direct  calorimetric  method  involves  the  combustion  of  the 
fuel  by  oxygen  supplied  either  as  free  oxygen  gas  or  as  combined 
oxygen  of  some  chemical  compound,  the  operation  being  carried 
out  in  a  closed  vessel  immersed  in  a  known  mass  of  water  under 
conditions  which  ensure  that  the  heat  evolved  in  the  oxidation 
shall  be  with  as  little  loss  as  possible  transferred  to  and  retained 
by  the  calorimetric  vessel  and  the  water.     The  heat  evolved  is 
calculated  from  the  rise  in  temperature  of  the  system. 

Modern  methods  of  calorimetry  really  commenced  with  the 
invention  by  Berthelot  of  his  bomb  calorimeter  described  in 
188 1.1  This  has  become  the  standard  method  for  the  determin- 
ation of  heating  values  and  therefore  the  whole  of  this  chapter 
is  devoted  to  it.  Other  methods,  especially  that  of  Parr,  are 
described  in  the  following  chapter. 

2.  The  Calorimetric  Bomb. — Berfchelot  showed  that  if  com- 
bustion of  carbon  compounds  took  place  in  a  closed  vessel  in  an 
atmosphere  of  oxygen  compressed  to  at  least  seven  atmospheres 
and  with  a  weight  of  .combustible  such  that  only  30  to  40  per 
cent,  of  the  oxygen  initially  present  was  consumed,  combustion 
was  rapid  and  complete.     His  bomb  was  lined  with  heavy  plat- 
inum and  was  very  expensive.     Hempel  in  the  second  edition 
of  his  gas  analysis  published  in  1889  described  a  much  cheaper 
bomb  which  had  no  lining  and  which  has  been  found   to  be 
mechanically  unsatisfactory.     Mahler2  in  1892  reported  a  careful 
study  of  Berthelot's  method  as  applied  to  coals,  and  described 

1  Annales  de  Chimie,  5  Serie,  23,  160  (1881).     Annales  de  Chimie,  6  Serie, 
6,  546  (1885). 

2  Bui.  de  la  Societe  d.  Encouragement,  1892,  319. 

258 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    259 

a  bomb  of  improved  construction  with  an  enamel  instead  of 
a  platinum  lining.  This  bomb  is  mechanically  better  than 
HempePs,  but  there  is  still  the  objection  that  the  top  as  it  screws 
down,  roughens  the  gasket.,  Atwater1  in  1894  described  a  modi- 
fication of  the  calorimetric  bomb  distinctly  superior  mechanically 
to  the  preceding  iorms.  It  resembled  more  closely  the  Berthelot 
bomb  than  either  of  the  others  but,  whereas  the  Berthelot  bomb 
was  closed  by  a  tapered  plug  held  in  place  by  a  screwed  cap, 
Atwater's  was  closed  by  a  flat  cap  held  in  place  by  a  collar  slipped 
over  it  and  screwed  over  threads  on  the  outside  of  the  bomb 
after  the  manner  of  a  union  pipe-fitting.  In  this  way  all  tearing 
of  the  gasket  was  avoided.  The  Atwater  bomb  may  be  provided 
with  a  gold  or  platinum  lining.  Many  modifications  of  the 
calorimetric  bomb  have  been  made  by  other  workers,  but  the 
principle  has  not  been  changed.  Anyone  familiar  with  one 
instrument  can  readily  learn  to  use  any  other. 

3.  Details  of  the  Calorimetric  Bomb. — The  calorimetric  bomb 
which  has  been  in  use  in  the  calorimeter  laboratory  of  the  Uni- 
versity of  Michigan  since  1908  is  shown  in  Figs.  55  and  56.  It 
is  in  general  patterned  after  the  Atwater  bomb,  but  possesses 
several  improvements.  One  of  these,  due  to  Mr.  Edwin  H. 
Cheney,  is  the  octagonal  belt  on  the  body  of  the  bomb  which  fits 
into  a  recessed  plate  and  holds  the  bomb  rigidly  while  the  cover 
is  being  screwed  on.  Another,  due  to  Professor  S.  W.  Parr,  is 
the  deeply  recessed  groove  for  the  gasket  in  the  cover  of  the 
bomb  into  which  the  straight  lip  of  the  bomb  fits  closely  so  that 
a  rubber  gasket  may  safely  be  used.  Improvements  in  various 
details  are  due  to  Mr.  J.  H.  Stevenson,  instrument  maker  of 
the  University  of  Michigan.  Details  of  the  bomb  are  shown  in 
Fig.  55.  It  consists  of  a  cylinder  of  about  300  c.c.  capacity  on 
which  sits  a  cover  carrying  the  oxygen  inlet  and  needle  valve. 
The  original  models  were  made  of  steel  and  some  of  them  have 
withstood  continuous  use  by  classes  of  beginners  for  ten  years. 
They  become  coated  with  a  layer  of  dense  adherent  scale  on  the 
inside  and  after  that  show  very  little  change.  One  of  these 
bombs  was  cut  into  sections  after  ten  year's  use  and  showed  no 
measurable  decrease  in  thickness  of  the  metal  due  to  corrosion. 

1  Storrs  Conn.  Experiment  Station  Report,  1894,  135;  also  J.  Am.  Chem. 
Soc.,  25,  659  (1903). 


260 


GAS  AND  FUEL  ANALYSTS 


Monel  metal  was  soon  substituted  for  steel  as  the  material  from 
which  the  heads  were  made  to  avoid  corrosion  of  the  needle 
valve,  and  within  the  last  few  years  the  entire  bomb,  except  the 
collar,  has  been  made  of  monel  metal.  It  stays  bright  both 
inside  and  out  with  no  especial  care,  and  the  small  amount  of 
metal  dissolved  by  the  acids  formed  in  combustion  introduces 
only  a  negligible  error  in  the  calorimetric  work.  Compressed 
oxygen  is  admitted  through  a  flexible  metal  tube  soldered  at  A 


FIG.  55. — Details  of  calorimetric  bomb. 

to  the  steel  tube  with  the  coned  head  B.  This  tube  AB  slides 
freely  in  the  threaded  sleeve  C.  Its  coned  head  makes  a  gas 
tight  joint  with  the  bomb  when  C  is  screwed  up.  The  needle 
valve  D  closes  the  bomb  when  it  is  screwed  down.  The  coal 
sits  in  a  flat  nickel  or  quartz  capsule  E  supported  on  a  ring  which 
screws  into  the  head  piece.  The  insulated  electrical  connection 
FG  is  a  rod  coned  where  it  passes  through  the  head  piece  from 
which  it  is  insulated  by  a  bit  of  thin  rubber  tubing.  The  binding 
post  G  screwing  down  on  the  threaded  end  of  F  which  projects 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    261 

through  the  cover  pulls  the  cone  tightly  into  its  seat  and  makes 
a  gas  tight  joint.  A  mica  disc  placed  between  the  binding  post 
and  the  bomb  completes  the  electrical  insulation  of  the  electrode 
from  the  bomb.  The  gasket  which  fits  into  the  groove  H  may 
be  of  lead,  hard  fiber  or  rubber.  Rubber  gives  a  tight  joint 
with  the  least  pressure  of  the  spanner  and  is  therefore  to  be 
preferred.  If  it  is  cut  to  fit  the  groove  accurately  the  inner  lip 
of  the  bomb  projecting  into  the  recessed  head  will  effectually 
protect  it  from  the  hot  gases  evolved  in  the  bomb  during  com- 
bustion. 

Fig.   56  shows  the  various  parts  of  the  calorimeter.     Two 
bombs  are  shown,  one  assembled  and  one  taken  apart  and  with 


FIG.  56. — Bomb  calorimeter. 

the  head  sitting  on  a  stand  in  position  for  adjustment  of  the  fine 
iron  firing  wires.  The  nickel-plated  copper  can,  the  stirrer  and 
the  insulating  buckets  are  also  shown. 

The  insulating  buckets  as  shown  in  Fig.  56  consist  of  two  con- 
centric fiber  pails  with  air  in  the  space  between  them.  It  is  in 
some  ways  preferable  to  have  this  space  filled  with  water,  whose 
temperature  may  be  set  at  any  desired  point.  This  minimizes 
the  effect  of  draughts  in  the  room  and  enables  the  operator  to 
use  a  Beckman  thermometer  without  having  to  shift  its  zero 
when  the  room  temperature  fluctuates.  The  temperature  of  the 
water  must  not,  however,  be  so  far  below  room  temperature 


262  GAS  AND  FUEL  ANALYSIS 

that  dew  will  deposit  on  the  walls  of  the  calorimeter  vessel. 
When  a  water  jacket  is  thus  used  in  the  calorimeter,  it  should  be 
provided  with  a  stirrer  and  its  temperature  should  be  recorded. 
Where  a  large  number  of  calorimetric  determinations  are  to  be 
made  in  a  laboratory  the  multiple  unit  installation  designed  by 
the  Bureau  of  Mines1  may  profitably  be  installed. 

4.  Thermometers. — Thermometers  for  the  calorimeters  should 
be  made  especially  for  the  purpose  with  a  stem  long  enough  to 
allow  the  bulb  of  the  thermometer  to  be  opposite  the  center  of 
the  bomb  and  should  be  carefully  calibrated.     It  is  necessary 
that  it  be  possible  to  read  the  rise  in  temperature  to  at  least 
0.01°  C.     The  best  thermometers  are  those  of  the  Beckman 
type  with  a  scale  length  of  6°  and  a  zero  point  adjustable  between 
12°  and  25°.     This  type  of  thermometer  is  always  to  be  recom- 
mended where  the  calorimeter  room  is  of  relatively  constant 
temperature  so  that  it  is  not  necessary  to  change  the  zero  point 
often.     Where  this  desirable  condition  is  not  fulfilled  calori- 
metric thermometers  with  a  fixed  scale  running  from  15°  to  30°  C. 
must  be  used.     These  are  usually  divided  only  into  0.02°  to 
avoid  the  excessive  length  of  stem  which  would  otherwise  result. 
The  thermometer  should  in  any  case  have  been  carefully  cali- 
brated since  an  error  of  0.01°  on  the  average  rise  of  3°  means  0.3 
per  cent,  or  approximately  40  B.t.u.  per  pound  of  coal. 

5.  Preparation  of  Sample. — The  methods  to  be  followed  in  ob- 
taining a  representative  sample  from  a  large  quantity  of  coal  and 
the  precautions  necessary  in  grinding,  sampling,  and  drying  this 
large  sample  have  been  given  in  Chapters  XIV  and  XV.     It  is 
assumed  here  that  the  sample  is  already  ground  to  a  fineness  of 
at  least  60-mesh  and  has  been  air-dried.     The  amount  of  mois- 
ture is  immaterial  so  far  as  the  operation  of  the  bomb  calorimeter 
is  concerned,  but  an  air-dried  sample  is  less  likely  to  change  during 
the  operation  of  weighing. 

When  powdered  bituminous  coal  is  burned  in  compressed  oxy- 
gen, combustion  is  so  violent  that  there  is  danger  that  gas  and 
even  solid  particles  will  be  projected  unburned  through  the  flame 
zone.  The  rate  of  combustion  may  be  materially  lessened  by 
reducing  the  surface  of  coal  exposed  to  the  oxygen.  This  is  best 
accomplished  by  briquetting  the  coal.  Most  bituminous  coals 

1  David  and  Wallace,  Technical  Paper  91,  Bureau  of  Mines  (1918). 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    263 

may  be  readily  compressed  into  pellets  in  a  screw  press.  The 
pressure  should  be  slowly  applied  and  allowed  to  remain  for  a 
few  minutes.  The  resulting  pellet  may  be  trimmed  to  approxi- 
mate weight  with  a  penknife.  It  is  advantageous  to  break  it 
into  two  or  more  pieces  and  discard  the  dust  before  weighing. 
The  advantage  of  cutting  the  pellet  lies  in  the  readier  ignition, 
for  pellets  which  have  been  pressed  very  hard  are  sometimes  so 
dense  on  the  surface  that  they  fail  to  ignite.  It  is  possible  to 
compress  some  bituminous  coals  so  firmly  on  the  surface  that 
the  gas  evolved  in  the  interior  of  the  briquette  by  destructive 
distillation  explodes  the  briquette  and  blows  a  cap  of  coke  out  of 
the  crucible.  If  these  dense  briquettes  are  cut  into  several 
pieces,  as  directed  above,  the  trouble  will  be  obviated.  It  is  not 
necessary  to  briquet  anthracite  coals  or  coke.  Indeed,  it  is  not 
possible  to  do  so  without  the  addition  of  a  binder  such  as  sugar 
or  bituminous  coal. 

6.  Manipulation  of  Bomb  Calorimeter. — The  bomb  is  taken 
apart  and  examined  to  see  that  it  is  in  good  condition  and  that 
the  gasket  is  not  cut.  A  few  drops  of  water  are  placed  in  the 
bottom  part  of  the  bomb  which  is  set  in  its  receptacle  in  the 
table-top.  The  top  part  of  the  bomb  is  placed  on  a  ring  of  an 
ordinary  ring  stand  as  shown  in  Fig.  56  which  allows  the  heavy 
terminals  to  drop  through  in  a  convenient  position  for  adjust- 
ment of  the  fuse  wire  and  sample.  The  weighed  sample  of  coal 
is  placed  on  a  shallow  thin  quartz,  nickel  or  platinum  capsule 
resting  on  the  supporting  ring  suspended  from  the  head  of  the 
bomb.  The  capsule  must  be  almost  flat  to  allow  free  access  of 
oxygen  from  the  edges  as  the  flame  flares  up.  Otherwise  com- 
bustion may  be  incomplete.  It  must  be  thin  or  it  will  chill  the 
flame  and  prevent  complete  combustion.  It  is  advisable  with 
anthracite  and  coke  to  place  a  thin  pad  of  ignited  asbestos  on 
the  metallic  capsule  in  order  to  decrease  still  further  the  cooling 
effect  of  the  metal. 

A  measured  length,  preferably  not  more  than  two  inches,  of 
the  fine  iron  ignition  wire  34  B.  &  S.  gage  is  attached  to  the 
heavy  wire  terminals  by  winding  the  ends  of  the  fine  wire  several 
times  around  the  heavy  ones,  leaving  the  fine  wire  in  the  form  of 
a  loop  between  the  terminals.  After  making  connections  the 
loop  is  pushed  down  until  it  rests  on  the  fragments  of  coal.  Care 


264  GAS  AND  FUEL  ANALYSIS 

is  to  be  taken  that  the  wire  does  not  touch  the  metal  capsule 
and  form  a  short  circuit. 

The  cover  with  the  sample  in  position  is  placed  carefully  on 
the  bomb  and  the  threaded  collar  slipped  over  it  and  screwed 
down,  pressure  finally  being  applied  with  the  spanner.  A 
novice  will  nearly  always  screw  the  cover  down  harder  than 
necessary,  thus  shortening  the  life  of  the  gasket.  A  moderate 
pressure  will  suffice  if  the  gasket  is  a  good  one.  Gaskets  cut 
from  ordinary  red  fiber  packing  are  too  porous  to  be  tight  unless 
screwed  down  with  great  pressure.  They  may  be  much  im- 
proved by  vacuum  impregnation  with  a  solution  of  5  grm.  of 
glue  in  5  c.c.  of  glycerine  and  100  c.c.  of  water.  After  impreg- 
nation the  gaskets  are  to  be  dried  in  air  and  rubbed  with  paraffine 
or  graphite  to  keep  them  from  sticking  to  the  metal. 

The  loose  joint  on  the  end  of  the  flexible  metal  tube  from  the 
oxygen  tank  is  screwed  into  the  head  of  the  bomb,  the  needle 
valve  of  the  bomb  opened  at  least  a  full  turn,  and  then  the  valve 
on  the  oxygen  tank  is  opened  slightly,  the  gas  entering  in  a 
slow  stream  from  the  tank  until  the  gage  shows  20  atmospheres 
pressure.  If  the  valve  on  the  tank  is  opened  relatively  more 
than  the  one  on  the  bomb  the  gage  between  the  two  may  show 
20  atmospheres  before  there  is  that  much  pressure  in  the  bomb. 
The  oxygen  valve  on  the  tank  is  to  be  closed  first  and  after  that 
the  valve  on  the  bomb.  If  the  valve  on  the  bomb  is  closed 
before  that  on  the  tank,  the  pressure  on  the  gage  will  rise  very 
quickly  to  the  full  pressure  of  the  oxygen  tank  which  may  be 
2000  Ib.  and  the  gage  may  be  blown  up. 

The  bomb  is  disconnected  and  placed  in  the  water  of  the 
calorimeter  or  in  a  separate  vessel  of  water  to  test  for  leaks.  If 
bubbles  of  gas  appear  around  the  threaded  ring  the  cover  must 
be  screwed  down  more  tightly,  and  possibly  the  gasket  may  have 
to  be  replaced.  If  bubbles  of  air  come  from  the  head  it  is  evi- 
dent that  the  needle  valve  is  leaking.  It  is  worse  than  useless 
to  try  and  force  it  to  become  tight  by  screwing  down  the  needle 
with  great  pressure  A  needle  valve  ground  truly  into  its  seat 
is  tight  with  slight  pressure.  If  a  particle  of  grit  comes  between 
the  metal  surfaces  the  application  of  pressure  causes  it  to  scour 
the  polished  surface  and  the  valve  will  leak  until  it  has  been 
again  ground  to  a  true  surface.  In  case  of  a  leaking  needle  valve 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    265 

the  pressure  must  be  relieved,  the  bomb  opened  and  the  needle 
valve  unscrewed  entirely  out  of  the  head.  The  lock  nut  into 
which  it  was  threaded  is  also  to  be  removed.  The  coned  seat 
into  which  the  needle  valve  is  ground  may  now  be  seen  in  a 
strong  light.  The  best  policy  is  to  grind  the  needle  valve  into 
its  seat,  an  operation  requiring  not  more  than  ten  minutes  if  the 
valve  has  not  been  abused.  The  needle  valve  is  dipped  into  a 
paste  of  fine  emery  or  carborundum  in  water  and  ground  into 
its  seat  by  rotating  it  back  and  forth  with  the  fingers.  A  polished 
ring  will  soon  be  visible  on  the  cone  point  and  a  corresponding 
ring  in  the.  seat.  When  this  appears,  unless  the  metal  has  been 
badly  scratched,  the  process  may  be  considered  complete  and 
the  grinding  interrupted.  The  valve  is  to  be  thoroughly  cleaned 
from  grit  and  dried,  when  it  is  ready  for  use. 

The  bomb  when  charged  is  to  be  carefully  centered  in  the 
calorimeter  vessel  which  is  in  turn  centered  in  the  outer  vessels. 
The  stirrer  and  thermometer  are  placed  in  position  and  two 
liters  of  water  whose  temperature  is  approximately  3°  below 
room  temperature  is  added.  A  glass  flask  which  holds  1000 
c.c.  of  water,  contains  the  following  weights  of  water,  when 
balanced  against  brass  weights  in  air.1 

15°  C 998.05  grm. 

20°  C 997 . 18  grm. 

25°  C 996.04  grm. 

30°  C 994.66  grm. 

The  liter  flasks  of  various  makers  differ  in  the  amount  of 
water  which  they  discharge  and  the  flask  should  be  calibrated 
by  direct  weight  for  some  one  temperature.  It  is  more  conven- 
ient for  calculation  purposes  to  calibrate  the  flask  to  deliver 
2000  grm.  of  water  at  the  temperature  most  frequently  used, 
or  sometimes  to  deliver  such  an  amount  of  water  that  the  sum 
of  the  water  added  and  the  water  value  of  the  calorimeter  shall 
be  2500  grm.  It  is  in  many  ways  better  to  weigh  the  water 
directly  into  the  counterpoised  calorimeter  vessel  as  it  sits  on 
the  balance. 

Especial  care  is  to  be  taken  to  see  that  the  thermometer  is 
centered  in  the  space  between  the  bomb  and  the  edge  of  the 

1  Bureau  of  Standards  Bull.  4,  600  (1907-08) 


266  GAS  AND  FUEL  ANALYSIS 

vessel.  If  it  touches  either,  or  even  if  it  is  a  little  off  center, 
the  rise  of  the  thermometer  will  not  be  even  and  the  result  may 
be  in  error. 

After  the  adjustments  are  complete  the  stirrer  is  operated  for 
at  least  two  minutes  before  the  first  temperature  reading  is 
made  on  an  even  minute.  Readings  are  to  be  made  each  minute 
thereafter  for  at  least  five  minutes,  the  stirrer  being  kept  going 
steadily  at  30-40  strokes  per  minute  and  the  temperature  slowly 
and  steadily  rising  with  each  reading  as  heat  is  absorbed  from 
the  air  of  the  room,  or  dropping  if  the  calorimeter  is  above  room 
temperature.  This  ends  the  preliminary  period,  which  must 
show  at  least  five  readings  changing  by  regular  increments  due 
solely  to  heat  transfer  to  or  from  the  outside  air. 

The  firing  circuit  is  closed  simultaneously  with  the  last  read- 
ing of  the  preliminary  period.  The  iron  wire  becomes  heated 
to  redness,  the  coal  ignites  and  the  iron  wire  fuses  almost  in- 
stantly. It  is  well  to  have  an  electric  lamp  in  the  firing  circuit 
which  lights  when  the  current  is  turned  on  and  is  extinguished 
when  the  wire  fuses.  An  ammeter  in  the  circuit  answers  the 
same  purpose  showing  that  the  ignition  is  prompt  and  that  an 
undue  amount  of  heat  is  not  imparted  to  the  calorimeter  by  the 
electric  current.  Current  for  ignition  may  best  come  from  a 
storage  battery  or  group  of  dry  cells  giving  about  12  volts. 
Higher  voltages  are  apt  to  cause  insulation  troubles. 

Within  a  half  minute  after  ignition  the  thermometer  begins 
to  rise  so  rapidly  that  it  is  not  possible  to  make  the  thermometer 
readings  accurately.  They  should  be  taken  as  accurately  as 
possible,  and  regularly  on  each  minute.  After  about  three 
minutes  the  thermometer  reaches  its  maximum,  but  the  stirring 
and  temperature  readings  must  be  kept  up  without  intermission 
for  a  total  of  ten  minutes  after  ignition  to  obtain  data  for  the 
radiation  corrections. 

After  the  termination  of  the  thermometer  readings  the  bomb 
is  removed  from  the  calorimeter,  wiped  dry,  and  placed  in  its 
receptacle  on  the  table.  The  needle  valve  is  opened  and  after 
the  pressure  is  relieved  the  top  is  removed.  The  coal  should  be 
perfectly  burned  and  the  ash  should  appear  as  fused  beads.  The 
iron  wire  has  burned  as  far  as  the  heavy  conductors  and  in 
accurate  work  the  length  of  the  wire  unburned  should  be  deter- 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    267 

mined  to  enable  the  proper  correction  to  be  made  for  the  weight 
of  wire  burned.  The  weight  of  wire  burned  comes  to  be  almost 
a  constant  for  each  operator  and  may  be  taken  as  such  in  ordinary 
work.  If  soot  appears  in  the  bomb  or  on  the  capsule,  the  deter- 
mination should  at  once  be  rejected.  With  inexperienced  ope- 
rators this  trouble  is  frequently  caused  by  opening  the  valve  on 
the  oxygen  tank  too  fast  when  filling  the  bomb,  with  the  result 
that  the  gage  on  the  connecting  tube  jumps  to  the  proper  reading 
before  the  indicated  pressure  is  reached  in  the  bomb.  If  trouble 
persists  it  may  be  necessary  to  increase  the  oxygen  pressure  to 
25  atmospheres.  The  bomb  is  to  be  rinsed  out  carefully  and 
unless  it  is  to  be  used  again  at  once,  is  to  be  dried  best  in  an 
oven  at  a  temperature  of  about  35-40°  C.  Careful  drying  is 
especially  necessary  unless  non-corrodible  alloys  are  used 
throughout  the  construction  of  the  bomb. 

7.  Thermometer  Corrections. — The  calorimetric  thermometer 
should  have  the  certificate  of  the  Bureau  of  Standards.     In  addi- 
tion to  the  corrections  indicated  on  the  certificate  as  inherent 
in  the  thermometer  on  account  of  variation  in  the  diameter  of 
the  capillary  tube,  etc.,  minor  corrections  must  be  made  in  ac- 
curate work  for  variations  due  to  the  conditions  under  which  the 
thermometer  is  used.     The  Bureau  of  Standards  calibrates  ther- 
mometers when  totally  immersed  in  a  bath  of  the  temperature 
indicated.     In  calorimetric  work  the  bulb  and  part  of  the  stem 
is  within  the  calorimeter,  while  part  of  the  stem  projects  through 
the  cover  of  the  calorimeter  into  the  air  of  the  room.     A  small 
correction  must  be  made  for  this  emergent  stem.     In  the  case 
of  Beckmann  thermometers  an  additional  ''setting  factor  correc- 
tion" must  be  used  in  case  the  thermometer  is  set  for  a  different 
zero  from  that  used  in  the  calibration.     The  formulae  for  these 
corrections  vary  with  different  sorts  of  glass  and  are  given  in  full 
in  the  certificate  of  calibration  accompanying  each  thermometer. 
The  corrections  rarely  amount  to  more  than  a  few  thousandths 
of  a  degree. 

8.  Radiation  Corrections. — The  combustion  of  the  coal  in  a 
bomb  calorimeter  is  probably  a  matter  of  only  a  few  seconds,  but 
it  requires  several  minutes  for  the  heat  to  be  transmitted  to  the 
water  and  for  the  thermometer  to  register  the  rise  in  temperature. 
With  the  usual  type  of  instrument  radiation  corrections  must 


268  GAS  AND  FUEL  ANALYSIS 

be  made  in  spite  of  careful  jacketing  of  the  calorimeter.  Their 
magnitude  is  lessened  by  adjusting  the  temperature  of  the  water 
placed  in  the  calorimeter  with  reference  to  room  temperature 
and  to  the  rise  in  temperature  expected.  If  the  rise  in  tempera- 
ture is  to  be  3°,  the  water  poured  into  the  calorimeter  should  be 
about  3°  below  room  temperature.  When  equilibrium  is  reached 
at  the  time  of  ignition  the  temperature  will  be  about  2.5°  below 
that  of  the  room  and  after  combustion  it  will  be  about  0.5°  above 
room  temperature.  This  arrangement  minimizes  the  errors. 
The  temperature  rises  very  rapidly  after  ignition  to  one  so  nearly 
that  of  the  room  that  changes  due  to  radiation  are  slight  and 
repeated  readings  may  be  made  to  obtain  the  final  temperature. 
If  the  final  temperature  of  the  calorimeter  is  slightly  above  that 
of  the  room  there  should  be  a  maximum  point  in  the  thermometer 
readings  with  a  slow  decrease  thereafter. 

It  is  common  practice  to  consider  that  the  actual  maximum 
thermometer  readings  represent  the  actual  maximum  tem- 
perature of  the  calorimeter,  but  it  is  not  a  safe  assumption, 
for  if  the  thermometer  bulb  is  unduly  close  to  the  bomb  or  if 
the  stirring  is  inefficient  the  thermometer  may  rise  too  high  and 
fall  rapidly  again  to  the  temperature  representing  the  true 
average  value  of  the  system,  after  which  it  will  change  slowly 
and  regularly  through  radiation.  It  is,  therefore,  unsafe  to  use 
the  maximum  temperature  in  calculations.  The  final  tempera- 
ture of  the  combustion  period  should  be  taken  only  after  sufficient 
time  has  elapsed  so  that  it  is  certain  that  the  system  has  come 
to  equilibrium.  Five  minutes  is  usually  sufficient. 

Radiation  corrections  are  based  on  the  principle  that  the  inter- 
change of  heat  between  the  room  and  the  calorimeter  is  propor- 
tional to  the  difference  in  the  temperature  between  them.  The 
temperature  of  the  room  is  assumed  to  be  a  constant  during  any 
one  operation  and  need  not  even  be  known.  The  formula  for 
the  correction  as  used  by  Regnault  and  developed  by  Pfaundler1 
is  somewhat  complicated  in  appearance,  but  is  simple  in  use. 

Regnault-Pfaundler  Formula. — Three  sets  of  temperature  read- 
ings are  to  be  made.  The  initial  set  must  not  start  until  after 
the  temperature  of  the  calorimeter  has  commenced  to  change 
regularly  due  to  radiation.  It  consists  of  at  least  five  readings 

1Poggendorfs  Annalen,  129,  115  (1866). 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    269 

made  one  minute  apart.  Only  the  first  and  last  readings  and 
the  time  interval  enter  into  the  calculation,  but  it  is  advisable  to 
record  the  intermediate  readings  as  a  check  on  the  accuracy  of  the 
two  important  ones  and  to  make  sure  that  the  change  of  temper- 
ature is  uniform  as  it  should  be.  At  the  moment  of  taking  the 
final  reading  of  the  initial  period  the  firing  key  is  pressed  and  the 
reading  just  taken  is  recorded,  both  as  the  final  reading  of  the 
initial  period  and  the  first  reading  to  the  combustion  period.  It 
is  to  be  marked  TO. 

During  the  combustion  period  readings  are  to  be  made  and 
recorded  regularly,  not  only  till  the  thermometer  reaches  its 
maximum,  but  also  till  it  is  certain  that  the  changes  in  tempera- 
ture are  again  due  solely  to  radiation.  This  period  may  be  five 
to  ten  minutes.  There  follows  a  final  period  of  five  minutes  to 
fix  the  radiation  losses  for  the  latter  portion  of  the  test. 

The  derivation  of  the  Regnault-Pf  aundler  formula  is  as  follows : 

Let  t  =  mean  temp,  of  initial  period. 
t'  =  mean  temp,  of  final  period, 
v  =  loss  per  time  interval  in  initial  period, 
v'  =  loss  per  time  interval  in  final  period. 
To,  TI,  T2,  Tn  =  temperature  readings  in  combustion  period. 
ti,  t2,    .    .    .    .  tn  =  average  temp,  of  each  interval  during  com- 
bustion period;  i.e.,  ti  =  -  -,  etc. 


0  A  a,          QJ.      or          A 

Fio.  57. — Diagram  showing  derivation  of  Regnault-Pf  aundler  formula. 

The  special  case  assumed  by  Pfaundler  is  one  where  the  initial 
temperature  is  only  slightly  different  from  room  temperature, 
giving  a  small  value  for  v.  The  final  temperature  is  considerably 
above  room  temperature  and  the  value  of  v'  is  larger  than  v. 
The  geometrical  construction  for  the  Regnault-Pf  aundler  formula 
is  shown  in  Fig.  57.  The  demonstration  is  as  follows: 


270  GAS  AND  FUEL  ANALYSIS 

Lay  off  OA  =  t. 
Lay  off  OA'  =  t'. 

LayoffOai  =  ti.         Oa2  =  t2  ....  Oan  =  tn 
At  A  erect  perpendicular  A  V  =  v. 
At  A'  erect  perpendicular  A'V  =  v'. 

Join  V  and  V  by  a  straight  line  and  at  ai  a2  .  .  .  .  an  erect 
perpendicular  intersecting  W. 
Any  ordinate  arVr  =  AV+pVr. 

A'V  —  AV 

On  account  of  similar  triangles  pVr  =  ---  T-T-/  —  pV. 

A  A 


C  =  the  algebraic  sum  of  all  the  ordinates  =  correction  sought. 
n  =  the  number   of   observations  in   the   combustion   period 
proper. 

'  — 

...  tn-nt). 


Heat  received  by  the  calorimeter  from  the  outside  air  is  con- 
sidered as  negative  and  therefore  in  the  especial  case  assumed  by 
Pfaundler  where  the  initial  temperature  was  slightly  under  room 
temperature  v  was  negative. 

The  correctness  of  the  formula  is  independent  of  the  relative 
values  and  signs  of  v  and  v'. 

The  corrected  rise  in  temperature  of  the  calorimeter 

R  =  Tn-T0+C 

The  need  of  an  elaborate  correction  for  radiation  is  naturally 
less  when  the  calorimeter  is  provided  with  an  adequate  stirrer 
so  that  the  heat  interchange  between  the  bomb  and  the  water  is 
quickly  effected,  and  also  less  when  the  insulating  jacket  is  good 
than  when  it  is  poor.  With  a  well  designed  calorimeter  the 
largest  part  of  the  rise  in  temperature  occurs  in  the  first  minute 
and  if  the  final  temperature  is  only  slightly  above  room  tempera- 
ture radiation  in  succeeding  minutes  is  almost  negligible.  The 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER     271 

standard  method  of  the  American  Society  for  Testing  Materials 
prescribes  that  a  turbine  stirrer  shall  be  used  because  it  stirs 
more  efficiently  than  a  reciprocating  stirrer. 


SAMPLE  OF  RECORD 

Determination  of  Heating  Value  of  Coal  in  Bomb  Calorimeter. 
Sample  No.  U.  38         Date  Nov.  10,    ' 
Calorimeter  No.  2         Thermometer  No.  4 
Water  Value  of  Calorimeter  475  grm. 

Water  Used  2000  c.c.  =  1995  grm. 


Total  water  equivalent  2470  grm. 

Sample  of  coal  (air-dried)  0.9922  grm. 
Thermometer  readings 


by  minutes 
19.68 
19.68 
19.69 
19.69 
19.69 
21.4 
22.58 


To 


22.95 

23.09 
23.11 


T2 


T4 
T6 


Factors 
v  =  -0.0025 
v'  =  +0.0025 
t  =  19.69 
t'  =  23.11 

T!+T2+T3+T4=90.0 
To  +  Ts  =21.4 


n  =5 

Thermometer  corrections 
Tn  =23.11-0.045  =23.065 
To  =  19.69-0.040  =  19.65 


23.11 
23  .  1  1 
23.  10 
23  .10 

=  5X  -0.0025  +        ll-i         (90.0+21.4-5X19.7)  =  +0.006°  C. 
R  =23.065  -19.65  +0.006=  3.421°  C. 
3.421  X2470  =  8450  calories 

Deduct  for  0.025  grm.  fuse  wire         40 
Deduct  for  1.0  per  cent,  sulphur 

(20  X.  9922)  =  20         60 


OO  QA 


8390  calories 
—  8455  calories  per  gram  of  air-dried  coal. 

u.yy^z 

8455X1.8  =  15,219  B.t.u.  per  pound  of  coal. 


272  GAS  AND  FUEL  ANALYSIS 

Proximate  Analysis  of  Coal 
Moisture  0 . 32  per  cent. 

Volatile  Matter         22.87  t    t 
Fixed  carbon  72.67  /    95'5  Per 

Ash  4.14% 


100.00 
Heat  evolved  per  pound  coal  dry  and  free  from  ash  =  — ggg-  =  15936  B.t.u. 

Radiation  Correction  by  the  Dickinson  Formula. — Dr.  H.  C. 
Dickinson1  has  worked  out  a  simple  method  for  determining 
radiation  corrections  whose  use  is  recommended  in  the  Standard 
Method  of  the  American  Society  for  Testing  Materials,2  from 
which  the  following  quotation  is  made: 

Observe  (1)  the  rate  of  rise  (rj  of  the  calorimeter  temperature  in 
degrees  per  minute  for  five  minutes  before  firing,  (2)  the  time  (a)  at 
which  the  last  temperature  reading  is  made  immediately  before  firing, 

(3)  the  time  (b)  when  the  rise  of  temperature  has  reached  six-tenths 
of  its  total  amount  (this  point  can  generally  be  determined -by  adding 
to  the  temperature  observed  before  firing  sixty  per  cent,  of  the  ex- 
pected temperature  rise,  and  noting  the  time  when  this  point  is  reached), 

(4)  the  time  (c)  of  a  thermometer  reading  taken  when  the  tempera- 
ture change  has  become  uniform  some  five  minutes  after  firing,  (5)  the 
final  rate  of  cooling  (r2)  in  degrees  per  minute  for  five  minutes. 

"  The  rate  TI  is  to  be  multiplied  by  the  time  b  —  a  in  minutes  and  tenths 
of  a  minute,  and  this  product  added  (subtracted  if  the  temperature  were 
falling  at  the  time  a)  to  the  thermometer  reading  taken  at  time  a.  The 
rate  r2  is  to  be  multiplied  by  the  time  c-b  and  this  product  added 
(subtracted  if  the  temperature  were  rising  at  the  time  c  and  later) 
to  the  thermometer  readings  taken  at  the  time  c.  The  difference 
of  the  two  thermometer  readings  thus  corrected,  provided  the  cor- 
rections from  the  certificate  have  already  been  applied,  gives  the 
total  rise  of  temperature  due  to  the  combustion.  This  multiplied 
by  the  water  equivalent  of  the  calorimeter  gives  the  total  amount  of 
heat  liberated.  This  result,  corrected  for  the  heats  of  formation  of 
nitric  and  sulphuric  acids  observed  and  for  the  heat  of  combustion  of 
the  firing  wire  when  that  is  included,  is  to  be  divided  by  the  weight  of 
the  charge  to  find  the  heat  of  combustion  in  calories  per  gram.  Calories 
per  gram  multiplied  by  1.8  give  the  B.t.u.  per  pound. 
Example: 

1  Jour.  Ind.  and  Eng.  Chem.  5,  525  (1913). 
Scientific  Paper  No.  230,  Bureau  of  Standards. 

2  A.  S.  T.  M.  Standard,  1918, 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    273 

OBSERVATIONS 

Water  equivalent  2550  grm. 
Weight  of  charge  1.0535 
Approximate  rise  of  temp.  3.2° 
60  per  cent,  of  approximate  rise  1.9° 

Time  Temp.  Corrected  temp. 

10-21  15.244°         (Thermometer  corrections  from  the  certificate.) 

22  15 . 250 

23  15.255 

24  15.261 

25  15.266 

(a)  26    15.272  15.276° 

Charge  fired 

(b)  27-12  17. 201 

(c)31  18.500°  18.497° 

32  18 . 498 

33  18.497 

34  18.496 

35  18.494 

36  18.493 

COMPUTATION 

fi  =0.028°  ^5  =0.0056°  per  minute,     b  —  a  =  1.2  minutes 

The  corrected  initial  temperature 

is  15.276°  +0.0056°  X  1.2  =  15.283°. 

r2=  0.007°  4- 5  =0.0014°  per  minute;  c-b  =3.8  minutes. 

The  corrected  final  temperature  is  18.497° +0.0014  X 

3.8 =18.502° 

Total  rise  18.502° - 15.283° , =  3.219° 

Total  calories  2550X3.219 =  8209 

Titration,  etc —  7 

Calories  from  1.0535  grm.  coal 8202 

Calories  per  gram 7785 

or  B.t.u.  per  Ib 14013 

In  practice,  the  time  b  —  a  will  be  found  so  nearly  constant  for  a  given 
calorimeter  with  the  usual  amounts  of  fuel  that  b  need  be  determined  only 
occasionally. 

9.  Corrections  for  Oxidation  of  Nitrogen. — When  coal  is 
burned  on  a  grate  minute  amounts  of  oxides  of  nitrogen  are 
formed  by  the  combination  of  some  of  the  nitrogen  of  the  air  and 
possibly  also  of  the  fuel,  with  the  oxygen  of  the  air.  At  the 

1  The  initial  temperature  is  15.27°;  60  per  cent,  of  the  expected  rise  is  1.9°. 
The  reading  to  observe  is  then  17.2°. 
18 


274  GAS  AND  FUEL  ANALYSIS 

higher  temperature  of  combustion  in  the  compressed  oxygen  of 
the  calorimeter  more  oxides  of  nitrogen  are  formed  and  account 
should  be  taken  of  the  heat  evolved  in  their  formation.  The 
heat  of  formation  of  aqueous  nitric  acid  from  nitrogen,  oxygen, 
and  water  is  represented,  according  to  Thomsen,  by  the  following 
equation. 

2N+  5O+  H20  =  2HNO3+  29800  calories. 

This  corresponds  to  1058  calories  per  gram  of  nitrogen  or  238 
calories  per  gram  of  HNOs.  The  American  Society  for  Testing 
Materials  adopts  the  value  230  instead  of  238.  The  nitric  acid 
formed  may  be  estimated  in  bombs  with  platinum  or  gold  linings 
by  rinsing  out  the  bomb  and  titrating  the  washings  with  standard 
alkali.  From  this  total  acidity  is  deducted  the  sulphuric  acid 
formed  and  the  balance  is  considered  nitric  acid.  The  amount 
of  nitrogen  oxidized  is  roughly  about  one  per  cent,  of  the  total 
nitrogen  present  whether  introduced  as  free  nitrogen  with  the 
oxygen  or  as  combined  nitrogen  of  the  coal.  The  correction  is 
not  usually  more  than  8  calories  and  may  be  considered  to  be 
offset  by  the  heat  absorbed  in  keeping  the  gases  in  the  calorimeter 
at  constant  volume.  (See  §  12.) 

10.  Corrections  due  to  Oxidation  of  Sulphur. — When  sulphur 
or  pyrites  burns  in  the  air  only  about  5  per  cent,  of  the  sulphur 
is  oxidized  to  SO3,  the  rest  of  it  remaining  as  SO2.     When  com- 
bustion takes  place  under  high  oxygen  pressure  in  the  bomb  calor- 
imeter a  much  larger  percentage  burns  to  SOa  and  correction 
must  be  made  for  it.     The  equations  are. 
S+  20  =  SO2  gas  +  69,100  calories 
S+  3O+  H20  (excess)  =  dilute  H2SO4+  141,100  calories. 

One  gram  of  sulphur  burning  to  S02  evolves  2165  calories  and 
to  dilute  H2S04  evolves  4410  calories.  There  should  therefore 
be  a  deduction  made  of  2245  calories  for  each  gram  of  sulphur 
thus  oxidized  in  the  bomb.  The  difficulty  is  enhanced  by  the 
fact  that  sulphur  may  be  present  in  coal  as  free  sulphur,  as  sul- 
phur in  organic  combination,  as  pyrites  or  as  calcium  sulphate 
and  that  the  corrections  will  vary  for  each  of  these  various  forms. 
For  free  sulphur  burning  to  H2SO4  the  correction  will  be  2245 
calories  per  gram  as  given  above,  for  sulphur  as  pyrites  2042 l 

1  Somermeier  J.  Am.  Chem.  Soc.,  26,  566  (1904). 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    275 

calories,  while  for  sulphur  as  gypsum  or  sulphate  of  iron  no  cor- 
rection is  to  be  made  since  it  is  already  in  the  oxidized  form. 

The  conditions  governing  the  oxidation  of  sulphur  in  the  bomb 
calorimeter  were  studied  by  Regester1  who  found  that  the  oxida- 
tion of  SO2  to  SOs  in  the  bomb  was  largely  a  function  of  the 
quantity  of  oxides  of  nitrogen  which  were  present.  The  oxides 
of  nitrogen  are  derived  in  part  from  the  combined  nitrogen  of 
the  coal  and  in  part  from  the  free  nitrogen  in  the  gases  contained 
in  the  bomb.  Commercial  oxygen  may  contain  very  little  nitro- 
gen and  therefore  the  air  which  is  originally  present  in  the  bomb 
should  not  be  flushed  out  but  should  be  left  in  the  bomb  to 
ensure  the  presence  of  a  sufficient  quantity  of  nitrogen  to  provide 
for  the  oxidation  of  the  sulphur.  It  is  customary  to  assume  that 
all  of  the  sulphur  in  coal  exists  in  the  form  of  pyrites  and  to 
deduct  two  calories  for  each  milligram  of  sulphur  in  the  sample 
of  coal.  This  procedure  is  not  above  criticism  for  Parr2  has 
shown  that  the  amount  of  sulphate  in  fresh  coal  may  be  as  high 
as  one  per  cent,  and  that  it  doubles  after  six  months  storage  of 
the  ground  sample  in  the  laboratory. 

A  source  of  error  which  should  be  considered  here  is  that  due 
to  the  possible  action  of  the  dilute  sulphuric  acid  formed  upon 
the  inner  surface  of  an  unlined  bomb.  A  steel  bomb  soon  be- 
comes coated  with  oxide  on  its  inner  surface  so  the  action  will 
be  between  iron  oxide  and  sulphuric  acid.  According  to  Thorn- 
sen  the  reaction  Fe2O3xH2O+  3H2SO4  (dilute)  evolves  33,840 
calories.  This  means  353  calories  for  each  gram  of  sulphur  in- 
volved or  3.5  calories  as  the  maximum  error  involved  for  1  grm. 
sample  of  a  coal  containing  1  per  cent,  of  sulphur.  If  the  acid 
acts  upon  steel  rather  than  iron  oxide  the  heat  evolved  is  even 
less.  The  error  from  this  source  is  totally  negligible.  An  ex- 
pensive calorimeter  lined  with  gold  or  platinum  is  unnecessary 
except  where  the  greatest  refinements  of  accuracy  are  sought. 

11.  Correction  Due  to  Combustion  of  Iron  Wire. — -The  iron 
fuse  wire  which  burns  to  Fe3O4  evolves  1600  calories  per  gram, 
or  1.6  calories  per  mg.  of  iron  burned. 

12.  Reduction   to   Constant   Pressure. — Combustion   in   the 
bomb  calorimeter  takes  place  at  constant  volume  whereas  in 

1  Jour.  Ind.  and  Eng.  Chem.,  6,  812  (1914). 

2  Jour.  Ind.  and  Eng.  Chem.,  5,  523  (1913). 


276  GAS  AND  FUEL  ANALYSIS 

ordinary  furnace  work  combustion  takes  place  at  constant  pres- 
sure. Wherever  a  decrease  in  volume  takes  place  on  combus- 
tion as  where  oxygen  unites  with  hydrogen  to  form  water  which 
condenses,  the  gases  in  the  calorimeter  which  should  normally 
have  contracted  after  combustion  have  had  work  done  upon  them 
to  keep  them  at  constant  volume  with  the  disappearance  of  an 
equivalent  amount  of  heat.  The  correction  amounts  to  541  cal- 
ories for  each  gram  molecule  of  gas  which  dissappears. 

When  gaseous  oxygen  combines  with  carbon  to  form  CC>2 
there  is  no  change  of  volume  and  hence  no  correction.  The  oxy- 
gen in  the  organic  matter  of  the  coal,  may  for  the  purposes  of 
this  calculation  be  considered  to  unite  with  the  hydrogen  of  the 
coal  to  form  water.  No  correction  is  needed  here  since  both  the 
hydrogen  and  the  oxygen  were  in  the  solid  state  before  combus- 
tion and  the  water  formed  is  a  liquid. 

There  is  always  present  in  coal  an  excess  of  hydrogen  over 
that  sufficient  to  combine  with  the  oxygen  and  this  so-called 
available  hydrogen  burns  with  gaseous  oxygen  to  form  water 
which  condenses  The  change  in  volume  is  shown  by  the  equa- 
tion 

4H(solid)+  02  =  2H2O  (liquid). 

The  gas  which  disappears  is  oxygen  in  the  proportion  of  one 
gram  molecule  for  each  4  grm.  of  hydrogen.  The  amount  of 
available  hydrogen  in  coals  varies  from  3  to  5  per  cent,  so  that 
on  a  gram  sample  there  would  be  on  an  average  0.04  grm.  of 
hydrogen  which  would  unite  with  0.01  grm.  molecule  of  oxygen 
causing  a  correction  of  5  calories — a  negligible  amount  except 
as  it  may  be  considered  as  balancing  other  minor  errors  such  as 
that  due  to  the  oxidation  of  nitrogen.  With  petroleum  the 
correction  will  be  about  three  times  as  great  as  with  coal. 

13.  Water  Value  of  Calorimeter. — When  combustion  occurs 
in  a  calorimeter  there  follows  a  rise  in  the  temperature  of  both 
the  water  and  of  the  calorimeter  vessel.  It  is  necessary  to  find 
how  many  calories  are  required  to  heat  the  metal  parts  of  the 
calorimeter  one  degree  and  when  this  has  been  accomplished 
the  value  is  translated  for  convenience  of  calculation  into  grams 
of  water  and  called  the  water  value  of  the  calorimeter.  The 
water  value  is  usually  determined  in  one  of  four  ways.  The  first 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    277 

is  by  calculation  from  the  weight  of  the  metal  parts  and  their 
specific  heats;  the  second  is  by  the  combustion  of  a  pure  sub- 
stance, such  as  sugar,  benzoic  acid  or  naphthalene,  whose  heating 
value  is  known;  and  the  third  is  by  the  addition  to  the  calori- 
meter of  a  definite  amount  of  hot  water  with  the  determination 
of  the  rise  in  temperature  resulting;  the  fourth  is  by  the  input 
of  a  definite  amount  of  electrical  energy.  The  first  method  is 
simple  but  of  only  approximate  accuracy.  The  second  method 
has  the  advantage  of  tending  to  compensate  for  any  errors  such 
as  the  oxidation  of  nitrogen  in  combustion  and  even  errors  in 
the  thermometer  and  in  radiation  corrections  in  so  far  as  these 
are  constant.  The  third  method  has  the  advantage  of  being  an 
absolute  one,  but  it  is  difficult  to  get  it  accurate.  The  fourth 
method  is  accurate  but  requires  considerable  equipment,  such 
as  described  by  Dickinson.1 

First  Method. — The  first  method  requires  simply  that  the 
weights  of  each  of  the  several  different  materials  contained  in 
the  bomb,  the  stirrer,  the  thermometer  and  the  water-containing 
vessel  be  known.  By  multiplying  these  weights  by  the  specific 
heats  as  given  in  the  following  table  the  number  of  calories  is 
obtained  directly. 

TABLE  OF  SPECIFIC  HEATS* 

Sp.  ht. 

Tool  steel. 0. 1087 

Gun  steel 0.1114 

German  silver 0 . 094 

Platinum 0 . 032 

Lead 0.030 

Oxygen  (constant  vol.) 0. 157 

Brass 0.094 

Mercury 0 . 033 

Glass 0.19 

The  inaccuracy  of  the  method  lies  partly  in  the  fact  that  it  is 
not  possible  to  determine  the  individual  weights  of  each  of  these 
constituents — e.g.,  the  mercury  in  the  thermometer,  and  partly 
in  the  fact  that  not  all  of  the  materials  thus  weighed  are  heated 
in  actual  practice  to  the  temperature  indicated  by  the  thermom- 

1  Scientific  Paper  No.  230,  Bureau  of  Standards. 

2  Atwater  and  Snell,  /,  Am,  Chem,  Soc.,  25,  694, 


278  GAS  AND  FUEL  ANALYSIS 

eter  immersed  in  water.  A  large  part  of  the  thermometer  is 
outside  of  the  calorimeter,  a  part  of  the  stirrer  is,  in  some  types 
of  apparatus,  constantly  passing  in  and  out,  and  the  top  of  the 
calorimeter  vessel  although  within  the  calorimeter  is  not  in  con- 
tact with  the  water.  On  the  other  hand  there  is  some  transfer 
of  heat  from  the  calorimeter  vessel  to  its  jackets  of  which  no 
account  is  taken.  Fortunately  all  these  errors  are  minor  ones 
but  the  method  can  hardly  be  considered  accurate  within  3  per 
cent. 

Second  Method. — The  method  of  determining  the  water  value 
of  a  calorimeter  by  the  combustion  of  a  substance  of  known  heat- 
ing value  is  the  most  commonly  employed  and  the  most  reliable 
one.  Sugar,  naphthalene  and  benzoic  acid  are  substances  which 
are  readily  obtained  in  a  state  of  purity  and  whose  heating  value 
has  been  determined  by  a  number  of  independent  observers. 
Dickinson1  has  accurately  determined  the  heats  of  combustion 
of  these  substances  and  gives  the  following  figures  as  the  heat  of 
combustion  per  gram  of  substances  weighed  in  air: 

Sucrose  3940  +  2  calories  (20°) 
Naphthalene  9622  +  2  calories  (20°) 
Benzoic  Acid  6329  +  2  calories  (20°) 

Benzoic  acid  is  recommended  as  the  most  desirable  for  a  com- 
bustion standard. 

The  procedure  in  determining  the  water  value  is  exactly  the 
same  as  for  the  combustion  of  a  fuel.  A  sufficient  amount  of 
the  pure  material  is  pressed  into  a  pellet  so  that  the  heat  evolved 
by  its  combustion  will  be  7000-8000  calories.  This  is  placed 
in  the  bomb  which  is  charged  with  oxygen,  set  in  the  calorimeter 
and  fired,  the  temperature  readings  being  made  as  usual.  In  the 
final  calculations  the  unknown  to  be  solved  for  is  the  mass  of 
water  equivalent  to  the  calorimeter  which  has  been  heated.  The 
difference  between  this  value  and  the  mass  of  water  actually 
added  gives  the  water  value  of  the  calorimeter. 

The  method  of  conducting  the  combustion  is  the  same  as  that 
for  coal  and  should  be  recorded  according  to  the  form,  §  8.  The 
following  example  gives  the  method  of  calculation. 

i  Scientific  Paper  No.  230,  Bureau  of  Standards  (1914). 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    279 

Total  heat  evolved 

from  benzoic  acid 1 .0856X6320  =  6870  calories 

from  iron  wire 0.022   X1600  =     35 

6905 

Corrected  rise  in  temperature  2.854°  C. 
Heat  absorbed  by  water  2000X2.854  5708 

Heat  absorbed  by  calorimeter  1197  calories 

1 107 
Water  value  =^^  =  419 

The  accuracy  of  this  process  is  dependent  first  on  the  purity 
of  the  materials  used  as  a  standard.  Samples  of  pure  substances 
with  certified  heat  value  should  be  obtained  from  the  Bureau  of 
Standards.  The  accuracy  is  also  affected  by  errors  in  the  ther- 
mometer, errors  due  to  oxidation  of  nitrogen,  etc.,  but  in  this 
very  fact  lies  one  of  the  valuable  points  of  the  method.  For  if 
it  be  assumed  that  with  a  thermometer  set  at  a  given  zero  there 
is  an  error  of  0.02°  in  a  rise  of  three  degrees  and  that  there  is  a 
correction  of  8  calories  to  be  made  with  oxygen  from  a  certain 
tank  when  a  sample  of  benzoic  acid  which  gives  a  rise  of  3°,  is 
burned,  and  both  of  these  corrections  be  neglected,  it  is  evident 
that  the  water  value  obtained  will  be  in  error.  But  if  this  erron- 
eous water  value  be  used  in  the  calculations  of  the  heating  value 
of  a  coal  where  the  errors  due  to  the  thermometer  and  the  oxi- 
dation of  nitrogen  are  the  same  as  in  the  combustion  of  sugar, 
and  where  the  total  rise  in  temperature  is  approximately  the 
same,  the  erroneous  water  value  will  compensate  for  the  errors 
on  the  coal  test  and  the  result  of  the  coal  test  will  be  correct. 

14.  Adiabatic  Calorimeters. — Corrections  for  transfer  of  heat 
between  the  calorimeter  and  its  jacket  must  always  be  made 
with  the  ordinary  type  of  instrument.  If  the  calorimeter  bomb 
is  placed  in  a  Dewar  vessel,  the  heat  interchange  may  be  lessened 
but  not  eliminated.  Corrections  may  only  be  avoided  by  com- 
pletely surrounding  the  calorimeter  by  a  vessel  whose  tempera- 
ture changes  constantly  during  the  test  to  keep  pace  with  the 
changing  temperatures  in  the  calorimeter.  The  temperature  of 
the  jacket  may  be  varied  by  addition  of  warm  water  or  by  elec- 
trical means.  Such  adiabatic  calorimeters  are  somewhat  com- 
plicated in  operation  but  allow  simple  calculations.  They  do 
not  necessarily  give  more  accurate  results. 


280  GAS  AND  FUEL  ANALYSIS 

15.  Precision  Calorimetry. — The  requirements  for  precision  in 
calorimetric  work  have  been  considered  by  Dickinson1  and  W.  P. 
White.2     It  is  useless  to  try  to  attain  precision  merely  by  in- 
creasing accuracy  of  thermometric  readings  as  by  substitution 
of  an  electric  for  a  mercurial  thermometer.     All  sources  of  error 
must  be  reduced  to  a  minimum  and  correction  must  be  made  for 
them.     When  it  is  considered  that  the  error  in  sampling  coal  is 
usually  over  one  per  cent.,  it  will  be  seen  that  methods  of  high 
precision  are  not  called  for  in  coal  calorimetry. 

16.  Accuracy  of  Results. — It  is  the  aim  to  determine  by  com- 
bustion in  the  bomb  calorimeter  the  amount  of  heat  which 
would  be  evolved  by  the  combustion  of  a  fuel  in  the  outside  air. 
This  standard  is  not  an  absolute  one,  for  not  only  will  carbon 
be  burned  to  carbon  dioxide  and  hydrogen  to  water  in  an  ordi- 
nary fire  but  also  sulphur  will  be  burned,  in  part  to  SO2  and  in 
part  to  SO3,  and  small  amounts  of  nitrogen  will  be  burned.     In 
applying  corrections  to  the  figures  obtained  in  the  bomb  calor- 
imeter it  is  customary  to  assume  that  all  of  the  sulphur  of  the 
coal  burns  to  SOs  in  the  bomb,  and  that  all  of  it  burns  to  SO2 
in  the  air,  and  that  no  nitrogen  is  oxidized  on  combustion  of 
coal  in  air.     The  errors  introduced  by  these  assumptions  are 
small  and  are  usually  neglected.     The  accuracy  of  the  estimation 
of  the  amount  of  heat  evolved  by  combustion  in  the  bomb  will 
depend  on  the  accuracy  with  which  the  water  value  of  the  system 
is  known,  the  care  taken  in  making  radiation  corrections  and  the 
accuracy  with  which  the  rise  in  temperature  is  measured.     This 
last  usually  involves  the  largest  error.     If  the  error  is  0.01°,  it 
will  amount  to  about  0.3  per  cent,  or  40  British  thermal  units. 
When  care  is  taken  in  every  detail  and  apparatus  of  superior 
quality  is  used  the  agreement  between  duplicate  determinations 
will  be  closer  than  this  but  it  is  certainly  not  safe  to  claim  a 
closer  absolute  accuracy  since  according  to  Jesse3  the  highest 
authorities  differ  by  0.25  per  cent,  as  to  the  absolute  heating 
value  of  sugar  and   benzoic   acid.     The  Committee  on   Coal 
Analysis   states   that  in   its   judgment  results  obtained  by  a 
single  analyst  should  not  differ  more  than  0.3  per  cent,  and  that 

1  Scientific  Paper  No.  230,  Bureau  of  Standards. 

2  Jour.  Franklin  Inst.,  186,  279  (1918). 

3  Jour.  Ind.  and  Eng.  Chem.,  4,  748  (1912). 

> 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER   281 

results  obtained  by  different  analysts  should  not  vary  by  over  0.4 
per  cent.  This  high  standard  can  only  be  attained  when  every 
precaution  is  observed. 

7.  Total  and  Net  Heating  Values. — The  heating  value  of  the 
fuel  computed  by  the  method  given  above  gives  the  total  heat 
developed  when  the  water  formed  condenses  to  a  liquid  within 
the  calorimeter.  This  gives  the  total  heat.  In  most  industrial 
operations  the  water  escapes  as  steam,  and  if  deduction  is  made 
for  its  latent  heat,  a  lower  net  heating  value  is  obtained.  This 
net  figure  gives  a  closer  approximation  to  the  heat  which  is  ordi- 
narily utilized,  but  it  does  not  give  it  accurately,  because  an 
arbitrary  assumption  has  been  made  as  to  the  temperature  of 
the  escaping  gases.  It  is  customary  to  report  the  total  heating 
value  of  the  coal  and  allow  the  consumer  to  put  such  a  factor 
on  it  as  will  indicate  its  relative  efficiency  for  the  purpose  to  which 
he  intends  to  put  it.  The  net  heating  value  is  obtained  by  de- 
ducting from  the  total  heating  value  the  latent  heat  of  the  water 
present  in  the  fuel  or  formed  in  combustion.  The  water  is 
determined  from  the  hydrogen  as  shown  by  ultimate  analysis. 
The  formula  for  calculation  of  net  heating  value  is: 

Net  heating  value  =  total  B.t.u.  — 1040  (hydrogen X9) 

Attempts  have  frequently  been  made  to  calculate  the  total 
heating  value  from  the  proximate  analysis.  Very  little  success 
has  attended  these  efforts,  but  Fieldner  and  Selvig1  have  shown 
that  the  correction  to  be  applied  to  the  total  heat  of  combustion 
to  obtain  the  net  heating  value  may  be  calculated  with  consider- 
able accuracy.  By  the  use  of  curves  constructed  from  2000 
analyses,  the  hydrogen  content  of  bituminous  coal,  semi-bitu- 
minous coal  and  anthracite  may  be  estimated  from  the  volatile 
matter  to  within  0.6  per  cent.  With  sub-bituminous  and  lig- 
nitic  coals  the  error  is  somewhat  greater.  The  original  paper 
must  be  referred  to  for  details. 

1  Technical  Paper  197,  Bureau  of  Mines. 


CHAPTER  XVII 

HEATING  VALUE  OF  COAL  BY  THE  PARR  CALORIMETER 
AND  OTHER  METHODS 

1.  Introduction. — -The  preceding  chapter  was  devoted  to  a 
discussion  of  the  bomb  calorimeter  as  the  standard  instrument 
for  the  determination  of  the  heating  value  of  coal.     The  present 
chapter  will  deal  with  other  methods,  such  as  combustion  in  a 
stream  of  oxygen,  combustion  with  chemicals  like  sodium  per- 
oxide, and  calculation  of  the  heating  value  from  the   chemical 
composition  of  the  coal. 

2.  Combustion  in  a  Stream  of  Oxygen. — Calorimeters  of  this 
type  have  become  obsolete  on  account  of  difficulties  of  manipu- 
lation and  sources  of  error.     The  temperature  of  the  oxygen 
flowing  in  must  be  accurately  measured  and  also  the  temperature 
of  the  gases  flowing  out,  for  correction  must  be  made  for  the 
heat  which  these  streams  of  gas  carry.     The  great  source  of  error 
is  the  incomplete  combustion  of  the  coal.     With  bituminous 
coals  smoke  may  frequently  be  seen  issuing  from  the  instrument 
and  even  with  anthracite  and  coke,  carbon  monoxide  may  always 
be  found  in  the  escaping  gases.     Accurate  results  have  been 
obtained  with  this  type  of  calorimeter  but  only  after  laborious 
correction  for  the  large  number  of  errors. 

3.  The  Thompson  Calorimeter. — A  very  crude  form  of  calor- 
imeter which  has  also  become  obsolete  was  that  of  Lewis  Thomp- 
son.    He  mixed  powdered   co'al  with  potassium   chlorate  and 
nitrate,  placed  the  mixture  in  a  calorimeter  vessel  and  fired  the 
charge.     The  method  and  apparatus  were  crude  throughout  but 
the  greatest  source  of  error  lay  in  the  heat  absorbed  in  the  de- 
composition of  the  chlorate  and  nitrate.     When  coal  burns  under 
a  boiler  it  unites  with  gaseous  oxygen  to  form  CO2  and  H2O. 
Essentially  the  same  result  takes  place  in  a  bomb  calorimeter. 
When,  however,  the  oxygen  is  taken  from  one  form  of  chemical 
combination  and  is  made  to  combine  with  the  coal  to  form  a 
different  compound,  the  result  is  not  at  all  the  same  as  that 

282 


HEATING  VALUE  OF  COAL  BY  THE  PARR  CALORIMETER     283 

obtained  in  the  combustion  of  the  coal  with  gaseous  oxygen  and 
the  corrections  to  be  applied  must  be  worked  out  with  great  care. 
Scheurer-Kestner1  determined  that  if  15  per  cent,  was  added  to 
the  heating  value  obtained  with  the  Thompson  calorimeter,  the 
results  never  differed  by  more  than  4  per  cent,  from  those  ob- 
tained by  the  Favre  and  Silverman  calorimeter  which  burns  the 
coal  in  a  stream  of  oxygen. 

4.  The  Parr  Calorimeter. — Parr2  proposed  sodium  peroxide  as 
a  chemical  to  be  used  in  oxidizing  coal  in  a  calorimeter,  worked 
out  the  corrections  to  be  applied,  and  devised  a  very  practical 
calorimeter.  He  writes  the  probable  reactions  in  the  calorimeter 
as  follows : 

2Na2O2+  C  =  Na2CO3+  Na2O 
Na2O2+  Na2O+  4H+  O  =  4NaOH. 

There  is  more  heat  evolved  in  each  of  these  reactions  than  in  the 
combustion  of  carbon  and  hydrogen  with  gaseous  oxygen  but 
fortunately  the  reduction  factor  is  closely  the  same  for  both  of 
them.  The  heat  evolved  by  the  combustion  of  carbon  and  hy- 
drogen in  the  Parr  calorimeter  multiplied  by  0.73  gives  the  true 
heat  value.  Smaller  corrections  are  to  be  made  for  the  dissocia- 
tion of  the  KClOs  used,  for  the  oxidation  of  sulphur,  the  com- 
bustion of  the  fuse  wire,  the  fusion  of  the  ash,  and  the  hydroxyl 
or  combined  water  present  in  coal. 

Since  the  oxygen  is  introduced  as  a  solid  and  the  Na2COa  and 
NaOH  formed  in  the  reaction  are  also  solids,  the  bomb  need  not 
be  made  to  resist  high  gas  pressures  but  may  be  made  of  thin 
metal. 

The  general  arrangement  of  the  calorimeter  is  shown  in  Figs. 
58  and  59.  Fig.  58  shows  a  section  of  the  fibre  buckets  which 
act  as  heat  insulators  and  of  the  can  which  holds  the  water.  The 
fusion  cup  is  shown  in  position.  The  stirring  is  accomplished 
very  effectively  by  the  removable  wings  attached  to  the  bomb 
which  force  the  water  down  the  annular  space  between  the  fusion 

1  Bull  Soc.  Ind.,  Mulhouse,  506,  1888. 
J  Jour.  Am.  Chem.  Soc.,  22,  646  (1900). 

Jour.  Am.  Chem.  Soc.,  24,  167  (1902). 

Jour.  Am.  Chem.  Soc.,  29,  1606  (1907). 

The  Chemical  Engineer,  6,  253  (1907). 

/.  Ind.  and  Eng.  Chem.,  1,  673  (1909). 


284 


GAS  AND  FUEL  ANALYSIS 


cup  and  the  centering  cylinder,  out  of  openings  at  the  bottom 
and  up  again  on  the  outside. 

Details  of  the  fusion  cup  are  shown  in  Fig.  59,  where  C  is  the 
brass  fusion  cup  closed  at  the  top  by  the  headpiece  and  the 
rubber  gasket  G.  The  outer  shell  A  and  the  removable  bottom 
B  are  separated  by  an  air  space  from  the  fusion  cup  which  pre- 
vents too  rapid  cooling  of  the  charge  during  the  first  stages  of 
fusion. 


FIG.  58. — Parr  calorimeter.          FIG.  59. — -Details  of  Parr  calorimeter. 

5.  Preparation  of  Parr  Calorimeter. — The  bomb  must  be 
thoroughly  dry  and  the  gasket  in  good  condition.  It  is  best  to 
dry  the  parts  after  each  test  in  an  oven  and  to  examine  them 
carefully  before  putting  them  together.  The  lower  cap  B  is 
fitted  into  place,  the  fusion  cup  is  inserted  in  its  shell,  and  the 
head  piece  firmly  screwed  down  with  the  wrench  provided. 
Water  leaking  into  the  bomb  always  spoils  the  determination 
and  may  cause  an  explosion. 


HEATING  VALUE  OF  COAL  BY  THE  PARR  CALORIMETER  285 

The  coal  is  to  be  ground  to  pass  a  100-mesh  sieve  in  order  that 
it  may  react  rapidly  with  the  peroxide.  Anthracite  coal,  coke, 
semi-bituminous  and  eastern  bituminous  coals  in  which  the 
moisture  will  not  exceed  3  per  cent,  may  be  used  in  an  air-dry 
condition.  Other  bituminous  coals,  lignites,  peats,  etc.,  must  be 
dried  at  105°  C.  before  use  to  avoid  the  reaction  between  the 
hygroscopic  moisture  and  the  peroxide  with  evolution  of  heat  in 
the  calorimeter.  The  danger  of  change  in  the  coal  sample  during 
the  processes  of  drying  and  grinding  is  treated  in  Chapter  XV  on 
Chemical  Analysis. 

It  is  necessary  to  secure  very  intimate  mixture  of  the  coal,  the 
Na2O2  and  the  KC103  added  as  an  accelerator  of  combustion. 
The  charge  consists  of  1  grm.  of  the  dry  and  finely  ground  KC1O3, 
0.5  grm.  of  the  coal  prepared  as  directed  above  and  approxi- 
mately 10  grm.  of  sodium  peroxide  which  may  be  measured  with 
sufficient  accuracy  in  the  scoop  provided  with  the  instrument. 
The  contents  of  the  bomb  are  next  to  be  thoroughly  mixed  by 
shaking.  If  this  were  done  after  the  regular  top  and  firing  wire 
were  in  place  the  firing  wire  would  almost  certainly  become 
twisted  and  short  circuited,  so  it  is  better  to  use  the  false  top 
provided.  It  is  well  at  the  beginning  of  the  shaking  process  to 
invert  the  cartridge  and  tap  it  sharply  on  the  desk  to  dislodge 
any  coal  which  may  have  stuck  to  the  bottom.  When  the  mixing 
is  complete  the  bottom  of  the  cartridge  may  be  tapped  lightly 
against  the  desk  to  dislodge  any  material  sticking  to  the  cap. 
The  regular  top  to  which  about  3  in.  of  fine  iron  wire  (32  or  34 
American  gage)  has  been  attached  in  a  loop  as  shown  in  Fig.  59 
is  now  placed  carefully  in  position  and  screwed  into  place.  Care 
should  be  taken  after  this  has  been  adjusted,  not  to  tip  the 
bomb  since  the  fine  iron  wires  are  easily  crossed.  The  spring 
stirring  clips  may  now  be  adjusted  and  the  apparatus  set  up  as 
shown  in  Fig.  58. 

The  strength  of  the  firing  current  will  vary  between  2  and  4 
amperes.  It  should  be  adjusted  by  trials  in  the  open  air  until 
the  wire  fuses  promptly  on  closing  the  switch. 

6.  Care  of  Sodium  Peroxide. — Sodium  peroxide  is  hygroscopic 
and  absorbs  moisture  from  the  air,  even  when  preserved  in  ap- 
parently well-stoppered  bottles,  forming  Na2O2.2H2O.  The 
effect  of  this  hydrate  formation  is  illustrated  by  an  experiment 


286  GAS  AND  FUEL  ANALYSIS 

made  by  Professor  Parr.  He  exposed  10  grm.  of  sodium  peroxide 
on  a  watch  glass  in  the  laboratory  for  an  hour  and  found  that  it 
had  gained  in  weight  nearly  0.5  grm.  This  peroxide  when  used 
in  the  calorimeter  gave  a  rise  in  temperature  higher  by  0.194° 
than  the  pure  peroxide.  As  the  total  correct  rise  of  temperature 
in  this  experiment  was  only  2.180°  it  will  be  seen  that  the  error 
was  almost  9  per  cent. 

The  sodium  peroxide  should  not  only  be  pure  and  anhydrous 
but  should  also  be  in  grains  of  the  proper  size.  If  the  peroxide 
is  too  coarse  the  powdered  coal  tends  to  sift  to  the  bottom  of  the 
bomb  and  escape  combustion.  If  peroxide  is  too  fine  the  reac- 
tion is  sometimes  very  violent.  The  manufacturers  of  the  calor- 
imeter furnish  reliable  peroxide  in  small  hermetically  sealed  cans 
and  also  furnish  a  clamp-top  fruit  jar  which  is  said  to  preserve 
the  contents  of  a  single  can  during  its  use. 

Sodium  peroxide  reacts  at  ordinary  temperatures  with  all 
organic  substances  in  presence  of  moisture  with  evolution  of 
heat  often  sufficient  to  produce  flame  or  explosion.  Mixtures  of 
sodium  peroxide  and  coal  which  may  have  to  be  disposed  of  are 
not  to  be  thrown  into  waste  jars.  They  may  be  cautiously  and 
slowly  poured  into  a  vessel  containing  considerable  water  which 
will  absorb  the  heat  and  prevent  violent  reactions.  Sodium 
peroxide  causes  bad  burns  on  the  skin. 

7.  Operation  of  Parr  Calorimeter. — The  fusion  cup  prepared 
as  above  directed  is  placed  in  the  calorimeter  vessel  and  properly 
centered.  Two  thousand  grams  of  water  are  then  added  to  the 
calorimeter  vessel.  It  is  preferable  that  the  temperature  of  the 
water  should  be  about  2.0°  C.  below  room  temperature  for  the 
radiation  correction  will  be  less  under  these  conditions.  The 
thermometer  is  adjusted  and  the  bomb  started  to  rotating  at 
the  rate  of  about  150  revolutions  a  minute.  Temperatures  are 
to  be  read  at  the  end  of  each  minute.  Within  two  or  three  min- 
utes the  readings  of  the  thermometer  should  become  almost 
constant  except  for  the  regular  and  very  slight  change  due  to 
radiation.  Should  the  thermometer  rise  irregularly  and  more 
rapidly  than  0.01  or  0.02°  per  minute  during  this  preliminary 
period,  there  is  probably  a  slight  leak  of  water  into  the  bomb. 
The  operation  must  be  at  once  stopped,  the  bomb  taken  out, 
wiped  dry  on  the  outside,  opened  and  emptied.  A  leaky  bomb  is 


HEATING  VALUE  OF  COAL  BY  THE  PARR  CALORIMETER     287 

not  only  inaccurate  but  dangerous.  After  five  readings  at  inter- 
vals of  one  minute  each  in  the  preliminary  period  have  shown 
only  this  slight  and  regular  change  of  temperature,  ignition  is 
effected  by  closing  the  switch  on  the  cover  of  the  instrument. 
The  thermometer  rises  very  rapidly  owing  to  the  thin  walls  of 
the  fusion  cup  and  the  efficient  stirring  and  usually  reaches  its 
maximum  after  two  minutes.  Nevertheless  observations  should 
be  continued  for  at  least  eight  minutes  after  ignition  to  allow 
corrections  for  radiation  to  be  made. 

The  bomb  is  then  removed  from  the  water,  wiped  dry  and 
opened.  There  should  be  no  trace  of  unburned  carbon  visible, 
nor  any  odor.  The  lower  plug  is  removed  and  the  inner  vessel 
with  its  fused  contents  placed  in  a  casserole  containing  about 
500  c.c.  of  water,  until  all  the  fused  peroxide  has  dissolved.  It 
is  then  removed,  rinsed  out  and  dried. 

The  solution  in  the  casserole  is  to  be  tested  for  unburned  car- 
bon. As  an  alkaline  solution  it  contains  black  flakes  of  oxides 
of  iron  and  copper.  After  acidification  it  becomes  a  clear  yellow 
solution,  with  carbon  as  the  only  matter  in  suspension,  the  silicic 
acid  remaining  in  solution  in  the  large  volume  of  water.  If  any 
unburned  carbon  is  visible  it  should  be  filtered  on  a  Monroe  or 
Gooch  crucible,  dried  and  weighed.  A  correction  of  8.1  calories 
must  be  made  for  each  milligram  of  unburned  carbon.  This 
precaution  should  never  be  omitted  by  a  beginner  nor  where 
accurate  work  is  important. 

The  corrected  rise  of  temperature  may  be  calculated  according 
to  the  formulas  given  in  Chapter  XVI,  but  a  simpler  method  will 
usually  suffice  since  this  calorimeter  is  not  used  where  the  great- 
est accuracy  is  required.  It  is  sufficiently  accurate  to  assume 
that  the  average  change  in  temperature  per  minute  during  the 
final  period  represents  also  the  change  due  to  radiation  for  each 
minute  during  the  combustion  period.  The  errors  involved  in 
this  assumption  are  small  since  the  temperature  in  the  combustion 
period  rises  to  almost  its  full  value  in  the  first  minute.  The  tem- 
perature at  the  end  of  the  fourth  minute  after  ignition,  may  be 
taken  as  the  end  of  the  combustion  period  and  corrections  as 
shown  by  the  next  four  minutes'  readings,  applied  to  it.  Cor- 
rections for  potassium  chlorate,  sulphur,  ash,  etc.,  as  given  in 


288  GAS  AND  FUEL  ANALYSIS 

the  following  section  are  to  be  deducted  from  this  reading,  the 
result  being  the  corrected  final  temperature. 

The  older  model  of  instrument  furnished  by  the  makers  had 
a  standard  water  equivalent  of  135  grm.  The  corrected  rise  in 
temperature  multiplied  by  2135  and  by  the  factor  .73  and  divided 
by  the  weight  of  the  sample  in  grams  gave  the  heat  value  in 
calories  per  gram.  The  figure  may  be  converted  into  British 
thermal  units  per  pound  by  multiplying  it  by  1.8.  The  present 
model  is  heavier  and  has  a  water  value  of  3100  grams  when 
ready  for  a  test. 

8.  Corrections  to  be  Applied  with  Parr  Calorimeter. — Parr  has 
worked  out  very  carefully  the  correction  to  be  applied  and  pub- 
lished his  results  in  the  journals  cited  as  references  at  the  com- 
mencement of  this  chapter.  He  has  shown  that  the  ratio  of  the 
heat  evolved  in  the  combustion  of  carbon  and  hydrogen  with 
gaseous  oxygen  to  that  evolved  on  combustion  with  sodium 
peroxide  is  very  closely  represented  by  the  factor  0.73.  The 
KClOs  used  as  an  accelerator  evolves  an  additional  amount  of 
heat.  Similar  corrections  are  required  for  ash,  sulphur,  fuse 
wire,  and  hydroxyl  constituents  of  the  coal.  Since  the  calor- 
imeter is  always  furnished  with  a  standard  water  value  these 
corrections  may  be  calculated  in  terms  of  temperature.  The 
corrections  for  the  earlier  model1  have  been  modified  to  conform 
to  the  altered  water  equivalent  of  the  new  apparatus  and  are 
now  given  as  follows : 

Electric  fuse  wire  equals 0.0030°  C.  or  0.005°  F. 

Per  cent,  ash  is  multipied  by 0.0025°  C.  or  0.005°  F. 

Per  cent,  sulphur  is  multiplied  by 0 . 0050°  C.  or  0 . 010°  F. 

1  gram  accelerator  equals 0. 1500°  C.  or  0.270°  F. 

Hydrogen  factors: 

For  all  Bituminous  coals 0 . 0400°  C.  or  0 . 070°  F. 

For  black  lignites 0.0560°  C.  or  0. 100°  F. 


9.  Accuracy  of  Parr  Calorimeter. — The  work  of  Professor  Parr 
has  shown  definitely  that  accurate  results  may  be  obtained  with 
this  calorimeter,  but  it  has  also  shown  that  this  accuracy  can  be 
gained  only  by  the  observation  of  precautions  and  the  use  of 
corrections  which  deprive  the  process  of  much  of  the  simplicity 

1  J,  Ind,  and  Eng.  Chem.,  1,  673  (1909). 


HEATING  VALUE  OF  COAL  BY  THE  PARR  CALORIMETER    289 

which  formerly  characterized  it.  Accurate  results  are  dependent 
on  the  quality  of  the  peroxide  used,  a  point  which  must  usually 
be  taken  on  faith.  The  calculations  involve  a  knowledge  of  the 
ash,  sulphur,  and  volatile  matter  of  the  coal  and  the  application 
of  corrections  for  these  constituents.  These  points  prevent  the 
method  from  being  a  standard  one  as  is  combustion  in  the  bomb 
calorimeter,  but  do  not  prevent  it  from  being  a  useful  commercial 
instrument  where  the  highest  accuracy  is  not  required. 

10.  Calculation  of  the  Heating  Value  from  Chemical  Analysis. — 
If  an  ultimate  analysis  is  available,  the  heating  value  of  a  coal 
may  be  calculated  with  fair  accuracy  from  the  Dulong  formula 
which  is  usually  given  as 

8080C+34460  fe~§)  +2500S 
Calorific  power  =  — 

JLUU 

where  C,  H,  0  and  S  represent  the  respective  percentages  of 
these  various  elements  shown  by  the  analysis.  This  formula 
gives  results  in  Calories  per  kilogram  which  when  multiplied  by 
1.8  are  converted  into  British  thermal  units  per  pound.  Tests 
of  57  coals  made  by  the  U.  S.  Geological  Survey1  show  an  average 
error  of  87.5  calories  in  the  calculated  result  and  a  maximum 
error  of  312  calories.  Inasmuch  as  it  is  much  simpler  to  deter- 
mine the  calorific  value  directly  than  to  make  an  ultimate  analy- 
sis, the  value  of  this  formula  has  come  to  lie  largely  in  its  confir- 
mation of  the  correctness  of  the  ultimate  analysis. 

A  formula  which  would  correlate  proximate  analysis  and 
heating  value  would  be  much  more  useful,  but  on  account  of  the 
variable  composition  of  the  volatile  matter  in  different  types  of 
coal  no  general  formula  can  be  devised  which  will  fit  all  cases. 
The  combustible  matter  of  coal  from  a  given  seam  is,  however, 
quite  constant  in  composition  and  after  its  value  has  been  experi- 
mentally determined  this  figure  may  be  used  with  considerable 
accuracy  as  a  basis  for  the  calculation  of  the  heating  value  of 
similar  coals  whose  moisture  and  ash  content  are  known. 

1  U.  S.  G.  S.,  Professional  Paper  48  (1906);  Bulletin  382  (1909)  p.  24. 


19 


290 


GAS  AND  FUEL  ANALYSIS 


TABLE  I.— SATURATION  PRESSURE  OF  WATER  VAPOR 


From  0-50°  C. 
Phys.  (4),  31,  731 


in  millimeters  of  mercury. 
(1910). 


Scheel  and  Heuse,  Ann.  d. 


Temp.°C.  I     mm.  Hg. 

Temp.0  C. 

mm.  Hg. 

0 

4.579 

26 

25.217 

1 

4.926 

27 

26.747 

2 

5.294 

28 

28.358 

3 

5.685 

29 

30.052 

4 

6.101 

30 

31.834 

5 

6.543 

31 

33  .  706 

6 

7.014 

32 

35.674 

7 

7.514 

33 

37.741 

8 

8.046 

34 

39.911 

9 

8.610 

35 

42  .  188 

10 

9.210 

36 

44.577 

11 

9.845 

37 

47.082 

12 

10.519 

38 

49.708 

13 

11.233 

39 

52.459 

14 

11.989 

40 

55.341 

15 

12.790 

41 

58.36 

16 

13.637 

42 

61.52 

17 

14.533 

43 

64.82 

18 

15.480 

44 

68.28 

19 

16.481 

45 

71.90 

20 

17.539 

46 

75.67 

21 

18.655 

47 

79.62 

22 

19.832 

48 

83.74 

23 

21.074 

49 

88.05 

24 

22.383 

50 

92.54 

25 

23.763 

APPENDIX 


291 


TABLE  II.— REDUCTION  OF  GAS  VOLUMES  TO  0°  AND  760  MM. 
MERCURY  PRESSURE  AND  DRYNESS 

If  the  gas  is  already  dry  the  reduction  formula  is 


1  +  . 00367  t  760 

where  t  is  the  temperature  and  h  the  barometric  pressure  corresponding  to 
the  volume  V. 

If  the  gas  is  saturated  with  moisture  there  must  be  deducted  from  the 
oberved  barometric  reading  the  value  e  for  the  yapor  pressure  of  water 
corresponding  to  the  temperature  t  as  given  in  Table  I.  The  reduction 
formula  then  becomes 


V0  = 


h-e 


1  +  .00367  t    760 


The  following  table  gives  the  values  for  l+0.00367t  for   each   degree 
from  0°  to  50°  C. 


t 

l+0.00367t 

t 

l+0.00367t 

0 

1.00000 

26 

1.09542 

1 

1.00367 

27 

1.09909 

2 

1.00734 

28 

1.10276 

3 

1.01101 

29 

1.10643 

4 

1.01468 

30 

1.11010 

5 

1.01835 

31 

.11377 

6 

1.02202 

32 

.11744 

7 

1.02569 

33 

.12111 

8 

1.02936 

34 

.  12478 

9 

1.03303 

35 

.  12845 

10 

1.03670 

36 

.  13212 

11 

1.04037 

37 

.  13579 

12 

1.04404 

38 

.  13946 

13 

1.04771 

39 

.  14313 

14 

1.05138 

40 

.  14680 

15 

1.05505 

41 

.  15047 

16 

1.05872 

42 

.15414 

17 

1.06239 

43 

.  15781 

18 

1.06606 

44 

.  16148 

19 

1.06973 

45 

.  16515 

20 

1.07340 

46 

.  16882 

21 

1.07707 

47 

1.17249 

22 

1.08074 

48 

1.17616 

23 

1.08441 

49 

1.17983 

24 

1.08808 

50 

1  .  18350 

25 

1.09175 

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APPENDIX 


297 


TABLE  V.— CORRECTIONS,    IN  B.t.u.,  TO    BE    APPLIED    TO 

OBSERVED  HEATING  VALUES  IN  CALCULATING  TOTAL 

HEATING  VALUES  OF  ILLUMINATING  GAS 

(ABOUT  600  B.t.u.)1 

(The  tabular  corrections  are  applicable  when  inlet  water,  air,  gas,  and 
products  are  all  at  approximately  the  same  temperature,  and  when  the 
calorimeter  is  operated  at  normal  rate  of  gas  consumption.  For  definition 
of  normal  rate,  see  p.  101.) 


Relative  humidity  of  air 

Temperature 

of  room, 

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

etc.  deg.  F. 

per 

per 

per 

per 

per 

per 

per 

per 

per 

per 

cent. 

cent. 

cent. 

cent. 

cent. 

cent. 

cent. 

cent. 

cent. 

cent. 

40 

+  2 

+  2 

+   1 

+  1 

+  1 

+  1 

0 

0 

0 



45 

+  2 

+  2 

+  2 

+  1 

+  1 

+  1 

0 

0 

0 

_ 

50 

+  3 

+  3 

+  2 

+2 

+  1 

+  1 

0 

0 

0 

— 

55 

+  3 

+  3 

+  3 

+2 

+  1 

+  1 

+  1 

0 

0 

_ 

60 

+  4 

+  4 

+  3 

+2 

+2 

+  1 

+  1 

0 

0 

_ 

65 

+  5 

+  4 

+  4 

+3 

+2 

+2 

+  1 

0 

-1 

-1 

70 

+  6 

+  5 

+  4 

+3 

+3 

+2 

+  1 

0 

-1 

-2 

75 

+  7 

+  6 

+  5 

+4 

+3 

+2 

+  1 

0 

-1 

-2 

80 

+  8 

+  7 

+  6 

+5 

+4 

+3 

+  1 

0 

-1 

-2 

85 

+10 

+  9 

+  7 

+6 

+4 

+3 

+2 

0 

-1 

-3 

90 

+  12 

+  10 

+  9 

+7 

+5 

+4 

+2 

0 

-2 

-3 

95 

+  14 

+  12 

+  10 

+8 

+6 

+4 

+2 

0 

-2 

-4 

1  Technologic  Paper  36,  Bureau  of  Standards. 


298 


GAS  AND  FUEL  ANALYSIS 


TABLE  VI.— CORRECTIONS,  IN   B.t.u.,  TO   BE   APPLIED   TO 

OBSERVED  HEATING  VALUES  IN  CALCULATING  TOTAL 

HEATING  VALUES  OF  NATURAL  GAS  (ABOUT 

1000  B.t.u.)1 

(The  tabular  corrections  are  applicable  when  inlet  water,  air,  gas,  and 
products  are  all  at  approximately  the  same  temperature,  and  when  the 
calorimeter  is  operated  at  normal  rate  of  gas  consumption.  For  definition 
of  normal  rate,  see  p.  101.) 


Relative  humidity  of  air 

Temperature 

of  room, 

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

etc.,  deg.  F. 

per 

per 

per 

per 

per 

per 

per 

per 

per 

per 

cent. 

cent. 

cent. 

cent. 

cent. 

cent. 

cent. 

cent. 

cent. 

cent. 

40 

+  4 

+  3 

+  3 

+  2 

+  2 

+  1 

+  1 

0 

0 

-1 

45 

+  4 

+  4 

+  3 

+  3 

+  2 

+  1 

+  1 

0 

0 

-1 

50 

+  5 

+  5 

+  4 

+  3 

+  3 

+2 

+  1 

0 

0 

-1 

55 

+  6 

+  6 

+  5 

+  4 

+  3 

+2 

+  1 

0 

-1 

-1 

60 

+  8 

+  7 

+  6 

+  4 

+3 

+2 

+  1 

0 

-1 

2 

65 

+  9 

+  8 

+  7 

+  5 

+  4 

+3 

+2 

0 

-1 

-2 

70 

+  11 

+  9 

+  8 

+  6 

+  5 

+3 

+2 

+  1 

-1 

-2 

75 

+  13 

+  11 

+  10 

+  8 

+  6 

+4 

+3 

+  1 

-1 

-3 

80 

+  15 

+  13 

+  11 

+  9 

+  7 

+5 

+3 

+  1 

-1 

-3 

85 

+  18 

+  16 

+  13 

+  11 

+  9 

+6 

+4 

+  1 

-2 

-4 

90 

+21 

+  19 

+  16 

+  13 

+  10 

+7 

+4 

+  1 

-2 

-5 

95 

+25 

+22 

+  19 

+  15 

+  12 

+8 

+5 

+  1 

-2 

-6 

Technologic  Paper  36,  Bureau  of  Standards. 


APPENDIX 


299 


TABLE  VII1.— EMERGENT  STEM  CORRECTIONS  TO  READING 

OF  OUTLET-WATER  THERMOMETERS  FOR  DIFFERENT 

IMMERSIONS  OF  THERMOMETERS  IN  CALORIMETER 

FOR  DETERMINING  HEATING  VALUE  OF  GAS 

(Table  applicable  when  temperature  of  inlet  water  is   approximately 
equal  to  room  temperature.) 


Temper- 

Temperature of  room 

ature 

rise  of 

water, 

50° 

60° 

70° 

80° 

90° 

100° 

deg.  F. 

10 

+0.02 

+0.03 

+0.04 

+0.05 

+0.05 

+0.06 

Thermometer  immersed  to  30°  F.  .  . 

15 

+0.04 

+0.05 

+0.06 

+0.07 

+0.09 

+0.10 

20 

+0.06 

+0.07 

+0.09 

+0.11 

+0.13 

+0.15 

10 

+0.01 

+0.02 

+0.03 

+0.03 

+  0.04 

+0.05 

Thermometer  immersed  to  40°  F.  .  . 

15 

+0.03 

+0.04 

+0.05 

+0.06 

+0.08 

+0.09 

20 

+0.04 

+0.05 

+0.07 

+0.09 

+0.11 

+0.12 

10 

+  0.01 

+0.01 

+0.02 

+  0.03 

+0.04 

+0.05 

Thermometer  immersed  to  50°  F.  .  . 

15 

+0.02 

+0.03 

+0.04 

+0.05 

+  0.07 

+0.08 

I    20 

+0.02 

+0.04 

+0.06 

+0.07 

+0.09 

+0.11 

10 

+0.00 

+0.01 

+0.02 

+0.02 

+0.03 

+0.04 

Thermometer  immersed  to  60°  F.  .  . 

1    15 

+  0.00 

+0.01 

+  0.03 

+0.04 

+0.05 

+0.06 

[   20 

+  0.00 

+0.02 

+0.04 

+0.05 

+0.07 

+0.09 

This  table  is  not  applicable  if  the  emergent  portion  of  the  stem  includes 
an  enlargement  in  the  capillary. 

Instead  of  using  the  above  table,  it  will  probably  be  somewhat  more  con- 
venient to  make  out  a  stem-correction  table  for  the  particular  outlet-water 
thermometer  that  is  to  be  used  with  the  calorimeter,  the  data  for  this 
separate  stem-correction  table  being  interpolated  from  the  above  table. 

Suppose,  for  example,  the  outlet-water  thermometer  to  be  used  was  one 
that  was  immersed  to  the  30°  F.  mark  on  the  scale,  and  a  stem-correction 
table  were  wanted  for  an  18°  F.  rise  in  temperature,  then  from  the  above 
table  we  obtain  the  following  stem-correction  table: 

STEM  CORRECTION  FOR  OUTLET-WATER  THER- 
MOMETER NO.— 

(Table  applicable  when  inlet  water  is  approximately  at  room  temperature, 
when  thermometer  is  immersed  to  the  30°  F.  mark,  and  when  the  tempera- 
ture rise  is  approximately  18°  F.) 


Inlet-water  tem- 
perature, deg.  F. 

Stem  correction, 
deg. 

Inlet-water  tem- 
perature, deg.  F. 

Stem  correction, 
deg. 

50 

0.05 

80 

0.09 

60 

0.06 

90 

0.11 

70 

0.08 

100 

0.13 

From  Circular  48,  Bureau  of  Standards. 


300 


GAS  AND  FUEL  ANALYSIS 


In  the  same  way  a  table  could  be  made  out  for  any  outlet-water  ther- 
mometer by  interpolation  in  the  general  table.  The  table  so  prepared 
would  apply  for  the  particular  point  to  which  the  thermometer  was  im- 
mersed and  for  the  particular  rise  in  temperature  with  which  the  observer 
had  chosen  to  work. 


TABLE    VIII.1— CORRECTIONS    FOR    DIFFERENCE  BETWEEN 

INLET-WATER  TEMPERATURE  AND  ROOM  TEMPERATURE 

IN  DETERMINING  HEATING  VALUE  OF  GAS 

(In  this  table  are  given  the  data  from  which  to  determine  the  amounts 
by  which  the  total  and  the  net  heating  values,  calculated  from  the  observed 
heating  value  as  if  the  inlet  water  had  been  at  room  temperature,  must  be 
corrected  on  account  of  any  difference  in  temperature  between  inlet  water 
and  room!  The  correction  calculated  from  this  table  may  be  applied  with- 
out sensible  error  to  heating  values  of  iluminating  gas  of  about  600  B.t.u. 
as  determined  with  any  of  the  flow  calorimeters  listed  in  this  circular  ex- 
cept the  Doherty  calorimeter.  The  correction  is  added  if  the  inlet  water 
is  warmer  than  the  room ;  subtracted  if  the  inlet  water  is  colder.  In  calcu- 
lating the  observed  heating  value,  the  stem  corrections  to  both  the  inlet 
and  outlet  water  thermometers  must  be  taken  into  account  when  the  inlet- 
water  temperature  differs  from  room  temperature.) 


Corrections,  in  B.t.u.  per  1°  F. 

Room  temperature, 

deg.  F. 

For  calculatng  total 

For  calculating  net 

heating  value 

heating  value 

50 

0.5 

0.4 

60 

0.6 

0.4 

70 

0.7 

0.4 

80 

0.8 

0.4 

90 

0.9 

0.5 

100 

1.0 

0.5 

1  From  Circular  48,  Bureau  of  Standards. 


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APPENDIX 


303 


TABLE  X.— MEAN  SPECIFIC  HEATS  OF  GASES  AT  CONSTANT 

PRESSURE  IN  B.T.U.  PER  CUBIC  FOOT  AT  60°  F.  AND  30  IN. 

OF  MERCURY  CALCULATED  FOR  THE  INTERVAL 

60°  F.-T 


T, 

deg.  F. 

Carbon  dioxide 

Water  vapor 

Nitrogen,  oxygen  and 
other    diatomic    gases 

200 

0.0237 

0.0220 

0.0174 

400 

0.0246 

0.0220 

0.0175 

600 

0.0253 

0.0221 

0.0177 

800 

0.0260 

0.0222 

0.0178 

1000 

0.0268 

0.0224 

0.0180 

1200 

0.0275 

0.0226 

0.0181 

1400 

0.0282 

0.0229 

0.0183 

1600 

0.0287 

0.0232 

0.0184 

1800 

0.0292 

0.0236 

0.0186 

2000 

0.0298 

0.0240 

0.0187 

2200 

0.0302 

0.0245 

0.0189 

2400 

0.0306 

0.0250 

0.0190 

2600 

0.0309 

0.0256 

0.0192 

2800 

0.0312 

0.0263 

0.0194 

3000 

0.0314 

0.0270 

0.0196 

3500 

0.0317 

0.0288 

0.0201 

4000 

0.0319 

0.0312 

0.0206     *^ 

TABLE  XL— MEAN  SPECIFIC  HEATS  OF  GASES  AT  CONSENT 

PRESSURE  IN  B.T.U.  PER  POUND  CALCULATED  FOR 

THE  INTERVAL  60°  F.-T 

T  I  Carbon  dioxide  |      Water  vapor      |         Nitrogen 


200°  F. 

0.2067 

0.4653 

0.2365 

400°  F. 

0.2143 

0.4657 

0.2386 

600°  F. 

0.2216 

0.4673 

0.2407 

800°  F. 

0.2285 

0.4698 

0.2428 

1000°  F. 

0.2348 

0.4735 

0.2449 

1200°  F. 

0.2406 

0.4782 

0.2470 

1400°  F. 

0.2462 

0.4841 

0.2491 

1600°  F. 

0.2512 

0.4910 

0.2512 

1800°  F. 

0.2559 

0.4990 

0.2534 

2000°  F. 

0.2601 

0.5081 

0.2555 

2200°  F. 

0.2638 

0.5182 

0.2576 

2400°  F. 

0.2670 

0.5294 

0.2597 

2600°  F. 

0.2698 

0.5420 

0.2618 

2800°  F. 

0.2722 

0.5557 

0.2639 

3000°  F. 

0.2742 

0.5702 

0.2660 

3500°  F. 

0.2770 

0.6093 

0.2707 

4000°  F. 

0.2790 

0.6599 

0.2755 

304 


GAS  AND  FUEL  ANALYSIS 


TABLE  XII.— VOLUME  OF  WATER  VAPORS  TAKEN  UP  BY  ONE 

CUBIC  FOOT  OF  AIR  WHEN  SATURATED  AT  VARIOUS 

TEMPERATURES 


Temperature 


Cubic  feet  of  water  vapor 


0°F. 
12°  F. 
22°  F. 
32°  F. 
42°  F. 
52°  F. 
62°  F. 
72°  F. 
82°  F. 
92°  F. 
102°  F. 


0.001 
0.002 
0.004 
0.006 
0.009 
0.013 
0.019 
0.027 
0.038 
0.053 
0.073 


TABLE  XIII.— COMPARISON  OF  THE  BAUME  SCALE  FOR 

LIQUIDS  LIGHTER  THAN  WATER  AND  SPECIFIC 

GRAVITIES 


Degrees 
Baum6 

Specific 
gravity 

Degrees 
Baum6 

Specific 
gravity 

Degrees 
Baum6 

Specific 
gravity 

10 

1.0000 

36 

0.8433 

62 

0.7290 

i 

0.9929 
0.9859 
0.9790 

37 
38 
39 

0.8383 
0.8333 
0.8284 

63 
64 
65 

0.7253 
0.7216 
0.7179 

14 

0.9722 

40 

0.8235 

66 

0.7142 

15 

0.9655 

41 

0.8187 

67 

0.7106 

16 

0.9589 

42 

0.8139 

68 

0.7070 

17 

0.9523 

43 

0.8092 

69 

0.7035 

18 

0.9459 

44 

0.8045 

70 

0.7000 

19 

0.9395 

45 

0.8000 

71 

0.6965 

20 

0.9333 

46 

0.7954 

72 

0.6931 

21 

0.9271 

47 

0.7909 

73 

0.6897 

22 

0.9210 

48 

0.7865 

74 

0.6863 

23 

0.9150 

49 

0.7821 

75 

0.6829 

24 

0.9090 

50 

0.7777 

76 

0.6796 

25 

0.9032 

51 

0.7734 

77 

0.6763 

26 

0.8974 

52 

0.7692 

78 

0.6731 

27 

0.8917 

53 

0.7650 

79 

0.6699 

28 

0.8860 

54 

0.7608 

80 

0.6667 

29 

0.8805 

55 

0.7567 

81 

0.6635 

30 

0.8750 

56 

0.7526 

82 

0.6604 

31 

0.8695 

57 

0.7486 

83 

0.6573 

32 

0.8641 

58 

0.7446 

84 

0.6542 

33 

0.8588 

59 

0.7407 

85 

0.6512 

34 

0.8536 

60 

0.7368 

90 

0.6364 

35 

0.8484 

61 

0.7329 

95 

0.6222 

SUBJECT  INDEX 


Absorption  methods  in  gas  analysis, 

28-42 
Acetylene, 

absorption  of,  85 
inhibiting      reaction     between 
phosphorus  and  oxygen,  32 
solubility  in  water,  85 
Adiabatic  coal  calorimeters,  279 
Air  and  water  vapor,  table  of  vol 

umes,  304 
Air, 

determination   of   relative   hu- 
midity, 113 
dissolved  in  water,   change  in 

composition,  7 
required  for  combustion  of  one 

pound  carbon,  150 
impure  affecting  candle  power, 

136 

Alcohol  as  fuel,  see  liquid  fuel 
Alkaline    pyrogallate,    reagent    for 

oxygen,  33 
Ammonia,  estimation  in  illuminating 

gas,  179 

Ammoniacal  copper  solution  as  re- 
agent for  oxygen,  35 
Amyl  acetate  for  photometric  pur- 
poses, 125 

Analysis,  see  coal,  gas,  etc. 
Argand  gas  burners,  128 
Argon  group  of  gases,  91 
Ash  in  coal,  composition,  230 
corrected,  257 
standard  method  of  analysis, 

245 

Aspirators,  5 

Automatic   instruments   for   analy- 
zing chimney  gases,  72 

Bar  photometer,  120,  132 

Barium    hydroxide    as    reagent    for 

carbon  dioxide,  84 
20  305 


Baume*  scale  for  liquids  lighter  than 
water,  table,  304 

Benzene  in  illuminating  gas,  166 
and   light   oils  in  illuminating 

gas,  167 

inhibiting      reaction      between 
phosphorus  and  oxygen,  32 

Benzoic  acid  as  standard  in  calori- 
metry,  278 

Blast  furnace  gases,  sampling,  144 

Bomb  calorimeter,  258 

see  also  heating  value  of  coal 

British  thermal  unit  defined,  104 

Bromine  water  reagent,  29 

Bulbed  gas  burette  for  exact  analy- 
sis, 79 

Bunte's  gas  burette,  68 

Burners,  standard  gas,  128 

Calculation  of  candle  power, 
of  explosion  analysis, 
of  heat  lost  in  chimney' 

150 

of  heating  value  of  coal,  273 
of  heating  value  of  gas,  103,  107, 

117 
of   volume   of   chimney   gases, 

146,  149 
Calibration  of  gas  burette,  22,  83 

of  gas  meter,  94 
Calorimeter,  see  heating  value, 
for  coal,  258 
for  gases,  97 
for  oils,  190 

Calory,  definition  of,  104 
Candle  power,  accuracy  of  photo- 
metric work,  137 
atmospheric    conditions    influ- 
encing, 137 
bar  photometer,  120 
Bray's  burner,  129 
Bunsen  screen,  129 


306 


SUBJECT  INDEX 


Candle  power,  calculation,  135 
candle  balance,  123 
candles  as  standards,  122 
decreasing  significance  of,    119 
details  of  a  test,  134 
Edgerton  standard,  127 
Elliot  lamp,  127 
equipment       of       photometer 

bench,  132 

flicker  photometer,  132 
gas  meter,  132 
Harcourt  lamp,  126 
Hefner  lamp,  123 
humidity  of  air,  136 
impure  air,  137 
incandescent  electric  standard, 

121 

jet  photometer,  137 
Leeson  screen,  129 
Lummer-Brodhum  screen,  129 
method  of  rating,  120 
Metropolitan  No.  2  burner,  129 
mtane  lamp,  126 
>meter  room,  136 
>metric  units,  122 
Sotometer  bench,  132 
saturating  water  of  meter,  132 
secondary  standards,  127 
setting  flow  of  gas,  135 
solubility  of  ilium  inants,  132 
standard  candles,  122 
standard  gas  burners,  128 
standard  lights,  121 
Sugg  D  burners,  127 
table  photometer,  121 
types  of  photometer,  119 
units,  120 
Capillary  tube  preventing  explosion, 

52 

Carbon  in  coal,  method  of  deter- 
mination, 251 

Carbon  dioxide,  determination  of,  28 
Carbon  dioxide,  formation  in  chim- 
ney gases,  145 

Carbon  dioxide,  recording  instru- 
ments for  chimney  gases, 
72 


Carbon  dioxide,  specific  heat,  table, 

303 

Carbon  monoxide,  causing  change  in 
blood,  86 

combustion  with  copper  oxide, 
56 

estimation  of  by  acid  cuprous 
chloride,  36 

estimation   of   by   ammoniacal 
cuprous  chloride,   38 

estimation  of  by  iodine  pento- 
xide,  86 

evolved  from  pyrogallate  solu- 
tion, 33 

explosion  analysis,  50 

formation  in  chimney  gases,  147 

fractional  combustion  with  cop- 
per oxide,  56 

fractional  combusion  with  pal- 
lodinised,  asbestos,  53 

hydrogen  and  methane,  simul- 
taneous explosion,  51 

initial  combustion  temperature, 
56 

incomplete  absorption,  37 

quiet  combustion  with  oxygen, 
51 

small  quantities  in  air,  60 
Carbonates  in  coal  ash,  230,  245 
Carbonic  acid,  see  carbon  dioxide 
Carbonic  oxide,  see  carbon  monoxide 
Carburetted  water  gas,  composition, 

165 

Caustic  soda,  reagent,  28 
Chemical  analysis,  see  coal,  gas,  etc. 
Chimney  gases,  144 

calculation  for  loss  of  heat  in, 
150 

calculation  of  volume  changes, 
146,  148 

carbon  dioxide  formation,  145 

carbon  dioxide  percentage,  154 

carbon  monoxide,  154 

carbon     monoxide     formation, 
147 

change  in  composition  in  con- 
tact with  water,  7 


SUBJECT  INDEX 


307 


Chimney  gases,  continuous  record- 
ing instruments  for  analysis  of, 

72 
effect  of  hydrogen  in  coal  on 

composition,  145 
interpretation  of  analysis,  153 
loss  of  heat  in,  150,  154 
loss  of  heat  due  to  water  vapor, 

151 

nitrogen  percentage,  154 
oxygen  percentage,  1M 
problem  illustrating  loss  of  heat 

in,  152 

sampling,  144 
solubility  in  water,  7 
specific  heats,  table,  303 
volume  of  air  per  pound  of  car- 
bon, 148 

volume  of,   per  pound  of  car- 
bon, 148 

Chollar  tubes  for  gas  analysis,  70 

Clinkering  properties  of  ash,  232 

Coal  analysis,  222 

accuracy  of  results,  238 
air-drying,  223 
air-drying  sample,  223 
ash  composition,  230 
ash  fusibility,  232 
ash,  standard  method  for,  245 
carbon,  total,  251 
combined  water  in,  151 
corrected  ash,  257 
deterioration  of  samples,  227 
Eschka  method  for  sulphur,  247 
fixed  carbon,  232,  247 
fusibility  of  ash,  232 
grinding  and  preserving  sample, 

25 

hydrogen,  251 
method  of  reporting,  237 
moisture,  227 

moisture,  standard  method,  243 
nitrogen,  237 

.       nitrogen,  standard  method,  255 
oxygen,  237,  256 
phosphorus,  237 
phosphorus  in  ash,  250 


Coal  analysis,  preliminary  examina- 
tion of  sample,  223 

preparation  of  laboratory  sam- 
ples, 240 

preservation  of  sample,  226 

proximate  analysis,  222 

slate  and  pyrites,  239 

standard  method,  240 

sulphur,  232 

sulphur,  standard  method.  247 

true  coal,  238 

ultimate  analysis,  236 

ultimate      analysis,      standard 
method,  251 

volatile  matter,  228 

volatile        matter,        standard 

method,  245 

Coal,  briquetting  sample  for  bomb 
calorimeter,  262 

changes  after  mining,  211 

changes  in  air-drying,  224 

chemical     analysis,     see     coal 
analysis 

combined    water,     percentage, 
151 

difference    in    composition     of 
lump  and  fine,  204 

effect  of  hydrogen  in,  on  chim- 
ney gases,  145 

grinding,  see  coal  sampling 

heating   value  of,   see  heating 
value 

washing,  239 
Coal  gas,  see  gas  analysis,  heating 

value,  candle  power,  etc. 
Coal  sampling,  204 

accuracy,  211 

a  scoopful  as  a  sample,  207 

difference    in    composition     of 
lump  and  fine  coal,  204 

from  cars,  209,  214 

from  wagons,  209,  214 

grinding  and  preserving  sample, 
218,  227 

influence  of  slate,  208 

mine  sampling,  209 

preparation  of  sample,  210,  215 


308 


SUBJECT  INDEX 


Coal      sampling,      preservation     of 

sample,  210,  218 
reducing  gross  sample,  215 
reliability  of  samples,  221 
standard  method,  214 
size  of  sample,  207,  215 
taking  of  sample,  209 
variation  in  results,  211 
washing,  239 
Coal  tar,  see  liquid  fuels, 
Coke,  chemical  analysis,  220,  257 
Coke,  sampling,  219 

specification  of  chemical  com- 
position, 221 
standard  method  for  chemical 

analysis,  257  • 

standard  method  of  laboratory 

sampling,  257 

Coke  oven  gas,  composition,  165 
Colorimetric  tar  determination,  142 
Combustion,  see  gas  analysis,  chim- 
ney gas,  producer,  gas,  etc. 
tabular  data  on  volumes,  heats, 

etc.,  302 
Constants  of  gases  and  vapors,  table, 

301,  302 

Continuous    recording    instruments 
for      analyzing      chimney 
gases,  72 
Conversion  factors  for  heating  value 

of  gas,  104 
Copper  oxide  method  of  fractional 

combustion,  56 

Copper  solution,  ammoniacal  as  re- 
agent for  oxygen,  35 
Corrections  in  gas  volume  for  tem- 
perature and  pressure,  75, 
95,  291,  292-5 
Cuprous  chloride, 
acid  solution,  36 
ammoniacal  solution,  38 
preservation  of,  36 
reagent  for   carbon  monoxide, 

36,  86 

reagent  for  oxygen,  35 
regeneration,  36 
Cyanogen  in  illuminating  gas,  179 


Diffusion,  errors  due  to,  84 

prevention  of,  84 
Distillation  test  for  gasoline,  200 
Dulong  formula,  289 

Electrical  precipitation  of  suspended 

particles,  143 
Ethane,  analysis  by  combustion  with 

copper  oxide,  59 
variation  from  gas  laws,  91 
Ethylene,  absorption  of,  29 

initial  combustion  temperature, 

56 

Exact  gas  analysis,  see  gas  analysis 
Explosion  analysis,  see  gas  analysis 
Explosion,  not  prevented  by  capil- 
lary tube,  52,  55 

Filters  for  solid  particles  in  gas,  141, 

142 

Fixed  carbon  in  coal,  analysis,  232 
standard  method  of  analysis, 

247 

Flash  point  of  oils,  193 
Flue  gases,  see  chimney  gases 
Form  of  record  of  gas  analysis,  61 

heating   value    of    gas,    105, 

109 
Fractional     combustion,      see     gas 

analysis 

Fuels,  liquid,  see  liquid  fuel 
Fuel  oil,  202 
Fuming  sulphuric  acid  for  olefines, 

29 
Fusibility  of  coal  ash,  232 

Gas,  analysis  of,  see  gas  analysis 
Gas,    candle   power   of,    see   candle 

power 
Gas,  heating  value  of,  see  heating 

value 
Gas,    suspended   particles,    see   gas 

analysis 

Gas,  table    of  properties,  301,  302 
Gas,  table  of  specific  heats,  303 
Gas,  see  also  illuminating,  natural, 

producer,  etc. 


SUBJECT  INDEX 


309 


Gas   analysis,    absorption   methods, 
28-42 

accuracy  of  technical,  27 

acetylene,  85    , 

alkalinity  of  burette  water,  26 

apparatus — Allen-Moyer  form, 

67 

Bunte's,  68 
Chollar's,  70 
Orsat's,  65 
White's,  16,  43,  77,  79 

calibration  of  burette,  22,  83 

carbon  dioxide,  28,  84 

carbon  monoxide  by  absorp- 
tion, 36 

carbon  monoxide  by  explosion, 
50 

carbon  monoxide,  hydrogen, 
and  methane  by  explosion, 
50 

carbon  monoxide  by  iodine  pen- 
toxide,  86 

combustion  methods,  43,  51 

continuous  recording  instru- 
ments, 72 

corrections  for  temperature  and 
pressure,  75 

details  of  simple  analysis,  25 

errors  due  to  diffusion,  84 

errors  in  explosion  of  hydrogen 
and  methane,  88 

exact  methods,  74-91 

explosion  analysis,  accuracy,  48 

explosion  analysis,  calculations, 
49 

explosion  pipette  details,  43 

explosion  analysis  manipula- 
tion, 46 

explosion  analysis,  hydrogen 
and  methane,  48 

form  of  record,  61 

fractional  combustion  with  cop- 
per oxide,  56 

fractional  combustion  with  pal- 
ladinised  asbestos,  53 

gas  burette,  simple,  16 

gas  burette,  bulbed,  79 


Gas  analysis,  gas  pipettes,  24 

general  methods,  14 

general  absorption  methods,  28 

general  scheme,  40 

historical,  74 

humidity,  table,  295,  296 

hydrogen  by  absorption,  38 

hydrogen  by  colloidal  palla- 
dium, 39 

hydrogen  by  explosion,  48,   87 

illuminating  gas,  163 

initial  combustion  temperature 
of  different  gases,  56 

methane  by  explosion,  50,  89 

minute  quantities  of  combusr 
tible  gas,  60 

natural  gas,  183 

nitrogen,  61 

olefines,  29,  85 

optical  methods,  73 

order  of  absorptions,  41 

explosion  analysis,  oxidation  of 
nitrogen,  47 

oxygen  by  explosion  or  combus- 
tion, 61 

oxygen,  30-35,  86 

oxygen,  commercially  pure,  32 

palladous  chloride  for  hydrogen, 
38 

pipettes,  White's,  24 

producer  gas,  158 

quiet  combustion  with  oxygen, 
51 

quiet  combustion  of  hydrocar- 
bons, 52 

recording  types  of  apparatus, 
72 

reduction  of  volume  to  standard 
conditions,  75,  291 

saturating  burette  water,   18 

suspended  particles,   138 

thermal  conductivity  methods, 
73  ' 

transferring  gas  from  holder,  19 

see  also  carbon  monoxide  and 
hydrogen  and  other  indivi- 
.dual  gases  ,, 


310 


SUBJECT  INDEX 


Gas  analysis,  table  of  constants  of 
certain  gases  and  vapors, 
301,  302 

tables  for  reduction  of  volume 

to  0°  and  760  mm.  dry,  291 

tables  for  reduction  of  volume 

to    60°    and    30    in.  wet, 

292-4 

tar  fog,  138 
unsaturated  hydrocarbons,  28, 

85 

variation  from  gas  laws,  90 
Gas  burette,  calibration,  22 
cleaning,  17 

description  of  simple  form,  15 
drawing  sample  of  gas,  18 
measuring  gas  volume,  21 
saturating  water  of,  18 
for  exact  analysis,  79 
see  gas  analysis 

Gas  burners,    standard   for   photo- 
metry, 128 
Gas  calorimeters,   continuous  flow, 

92-116 

automatic  and  recording,  117 
various  types,  116 
see  also  heating  value  of  gas 
Gas  holders,  for  samples,  13 

transferring  gas  for  analysis,  19 
Gas  mains,  sampling  from,  140 
Gas  meters,  calibration,  94 
description  of  wet,  93 
for  candle  power  tests,  132 
Gas  pipettes,  see  gas  analysis 
Gas  producers,  see  producer  gas 
Gas  Referees,  122,  126,  128 
Gas  sampling,  1-13 

apparatus  for  aspirating  sample 

of  gas,  9 
aspirators,  5 

collecting  average  sample,  8 
collecting  instantaneous  sample, 

11 

continuous  apparatus,  10 
errors  due  to  solubility,  7 
fair  sample,  1 
forms  of  sampling  tubes,  2 


Gas  sampling,  glass  gas  holders,  12 

illuminating  gas,  163 

influence  of  bends  in  mains  on 
suspended  particles,  140 

materials  for  sampling  tubes,  2 

point  of  mean  velocity  in  cross 
section  of  gas  main,  139 

producer  gas,  158 

saturating    water   in    sampling 
tubes,  8 

solubility  in  water,  6 

storage  of  samples,  1 1 

velocity  of  gas  in  sampling  tubes, 

140 

Gas  volume,  corrections  for  tempera- 
ture and  pressure,  95 

table  for  reduction  to    0°  and 

760  mm.  dry,  291 
60°  and  30  in.  wet,  292-4 

defined,  196 
Gasoline,  in  natural  gas,  185 

specifications,  197 

Heat  of  combustion,   table  for  va- 
rious materials,  301 
Heat  of  formation,  table  for  various 

materials,  302 
Heat  lost  in  chimney  gases,  150 

lost  in  chimney  gases  problem, 

152 

Heating  value  of  coal  in  bomb  calori- 
meter 

accuracy  of  results,  280 

action  of   acid  on   calorimeter 
bomb,  275 

adiabatic  calorimeters,  279 

calorimeter  bomb,  258 

calculation    of    heating    value, 
273 

correction    for    combustion    of 
iron  wire,  275 

corrections  for  oxidation  of  ni- 
trogen, 273 

corrections     for     oxidation     of 
sulphur,  274 

corrections  for  radiation,  268- 
273 


SUBJECT  INDEX 


311 


Heating    value    of     coal    in    bomb 

calorimeter 
details    of    calorimetric    bomb, 

259 

form  of  record,  271 
manipulation,  263 
net  heating  value,  281 
oxidation  of  nitrogen,  273 
oxidation  of  sulphur,  274 
precision  calorimetry,  280 
preparation  of  sample,  262 
radiation    corrections,    267-273 
Regnault-Pfaundler  formula, 

268 

Dickinson  formula,  272 
standard  method,  272 
reduction  to  constant  pressure, 

275 

sample  of  record,  271 
thermometers,  262 
thermometer  corrections,  267 
total  heating  value,  281 
water    value     of     calorimeter, 

276 

Heating  value  of  coal  in  Parr  calori- 
meter 

accuracy,  289 

care  of  sodium  peroxide,  285 
corrections,  288 
description,  283 
operation,  286 
Heating  value  of  coal  in  Thompson 

calorimeter,  282 
Heating  value  of  coal 

calculation       from       chemical 

analysis,  289 

combustion  in  a  stream  of  oxy- 
gen, 282 

general  method   of   determina- 
tion, 258 

peroxide  method,  283 
Heating  value  of  gas,  92-118 
accuracy  of  method,  108 
automatic  calorimeters,  117 
calibration  of  meter,  95 
calculated  from  chemical  com- 
position, 117 


Heating  value  of  gas,  calculation  of 

observed  heating  value,  103 

calculation     of     total     heating 

value,  107 
calculation  of  net  heating  value, 

106 
gas  calorimeters,  various  types 

see  gas  calorimeters 
conversion  factors  from  metric 

to  British  units,  104 
corrections  to  be  applied  to  ob- 
served   heating    value    of 
illuminating  gas,  table,  297 
corrections  to  be  applied  to  ob- 
served     heating  values  of 
natural  gas,  table,  298 
corrections    for    difference    be- 
tween inlet  water  tempera- 
ture   and    room    tempera- 
ture, table,  300 
corrections  for  emergent  stem  of 

thermometer,  table,  299 
corrections  for  temperature  and 

pressure,  95 

description  of  calorimeter,  97 
description  of  test,  102 
errors  itemized,  108 
form  of  record,  105,  109 
gross  heating  value,  106 
Hempel  calorimeter,  116    . 
humidity  of  air,  influence,  113 
illustrations  of  calculations,  105 
Junkers   calorimeter,    97 
measurement  of  mass  of  water, 

96 
measurement    of    temperature, 

96 

net  heating  value,  106 
normal  rate  of  gas  flow,  101 
observed  heating  value,  103 
preliminaries  of  a  test,  99 
recording  calorimeter,  117 
saturating  water  in  meter,   102 
Test  Record  of  Bureau  of  stand- 
ards, 109 

total  heating  value,  106 
uncondensed  water  vapor,  1 12 


312 


SUBJECT  INDEX 


Heating  value  of  liquid  fuels,  188 
Humidity    of    air,    affecting    candle 

power,  136 
Humidity  of  air,  determinations,  113 

relative  tables,  295,  296 
Hefner  lamp,  123 

Hydrogen,  accuracy  of  estimation 
affected  by  explosive  ratio, 
88 

analysis  by  absorption,  38 
carbon  monoxide  and  methane, 
simultaneous  explosion,  51 
affecting  compositions  of  chim- 
ney gas,  145 

method  of  analysis,  251 
fractional  combustion  with  pal- 

ladinised  asbestos,  53 
fractional      combustion      with 

copper  oxide,  56 
explosion  analysis,  48,  87 
initial  combustion  temperature, 

56 

quiet  combustion  with  air,  51 
Hydrogen  sulphide 

arsenious  acid  as  reagent,  72 
in  illuminating  gas,  169 
with  carbon  dioxide,  28 
Hydrometers,  comparison  of  Baum6 
scale    for     liquids     lighter 
than    water    and    specific 
gravity,  table,  304 
Hydrosulphite  as  reagent  for  oxygen, 
33 

Illuminants,  average  composition,  85 

solubility  of,  132 
Illuminating  gas,  163 

ammonia,  179 

benzene,  166 

benzene  arid  light  oils,  167 

candle  power,  see  candle  power 

chemical  composition,  164 

cyanogen,  179 

general  scheme  of  analysis,  164 

hydrogen  sulphide,  169 

naphthalene,  173 

sampling,  163 


Illuminating  gas,  scheme  of  analysis, 

164 

specific  gravity,  181 
suspended  tar,  179 
total   sulphur  compounds,    170 
typical  analyses,  165 
Incomplete  combustion  in  chimney 

'gases,  147 
Initial  combustion  temperatures  of 

various  gases,  56 
International  candle,  122 
Iodine  pentoxide  for  carbon  mono- 
xide, 61 
Iron,  heat  of  combustion,  275 

Jet  photometer,  137 

Kerosene,  flash  point,  193 

tests,  201 

Kjehldahl  method  for  nitrogen  in 
coal,  255 

Liquid  fuels,  187 

distillation  test,  198 

flash  point,  193 

fuel  oil,  202 

gasoline,  196 

heating  value,  188 

kerosene,  201 

moisture,  191 

proximate  analysis,  192 

sampling,  187 

specific  gravity,  191 

suspended  solids,  192 
Ix)ss  of  heat  in  chimney  gases,  150 
Lubricant  for  stop  cocks,  17 

Measuring  gas  in  burette,  21 

Meter  for  candle  power  determina- 
tion, 132 

Meter,  wet  gas,  93 

Methane,  accuracy  of  estimation 
affected  by  explosive  ratio, 
89 

carbon  monoxide  and  hydrogen, 
simultaneous  explosion,  50 


SUBJECT  INDEX 


313 


Methane,  by  combustion  with  copper 

oxide,  59 

by  explosion,  48,  89 
small  quantities  in  air,  60 
variation  from  gas  laws,  91 
initial  combustion  temperature, 

56 
quiet  combustion  with  air,   51 

Mine  air,  examination,  60 

Mine  sampling  of  coal,  209 

Moisture  in  air,  see  humidity 

Moisture  in  coal,  227 

standard  method  of  analysis, 
243 

Moisture  in  gas,  correction  for,  75 

Moisture  in  liquid  fuels,  191 

Naphthalene,   estimation  in  illumi- 
nating gas,  173 
estimation  in  tar,  176 
as     standard     in     calorimetry, 

278  ; 
Natural  gas,  analysis,  183 

analysis  by  fractional  distilla- 
tion at  low  temperatures, 
185 

errors  in  analysis  due  to  varia- 
tions from  gas  laws,  91 
typical  analysis,  184 
gasoline  vapors  in,  185 
specific  gravity,  182 
Net  heating  value  of  gas,  106 
Net  heating  value  of  coal,  281 
Nitrogen  in  gas  analysis,  61,  91 
Nitrogen  in  coal,  237 

method  of  analysis,  255 
Nitrogen,  oxidation  in  bomb  calori- 
meter, 273 
oxidation  in  explosion  analysis, 

47,  88 
table  of  specific  heats,  303 

defines,  absorption  of,  29 

estimation  of  mean  composi- 
tion, 85 

Optical  methods  in  gas  analysis,  73 
Orsat  apparatus,  65 


Oxidation  of  nitrogen,  error  caused 
by  in  gas  analysis,  47,  88 
corrections   for   in   coal   calori- 
metry, 273 
Oxygen,  always  present  in  industrial 

gases,  31 
analysis  of  commercially  pure, 

32 
determination  of  by  ammonia- 

cal  copper  solution,  35 
determination    of    by    alkaline 

pyrogallate,  33 
determination  of  by  hydrosul- 

phite,  33 

determination     of     by     phos- 
phorus, 30 

by  explosion  or  combustion,  61 

Oxygen    and    phosphorus,    poisons 

inhibiting  reactions,  29,  31 

Oxygen,    table    of     specific    heats, 

303 
Oxygen  in  coal,  237 

method  of  analysis,  256 

Palladinised  asbestos,  53 

Palladinised  copper  oxide  for  frac- 
tional combustion,  56 

Palladium,     colloidal     reagent     for. 
hydrogen,  39 

Palladous  chloride,  reagent  for  hy- 
drogen, 38 

Parr  calorimeter,  see  heating  value 

of  gas 

see  heating  value  of  coal 
see  liquid  fuels' 

Pentane,    combustion    with    copper 
oxide,  59 

Pentane  lamp,  126 

Permanganate    as    reagent   for    re- 
ducing gases,  84 

Peroxide,  sodium,  care  of,  285 

Peroxide  calorimeter,  see  Parr  calori- 
meter 

Peroxide  method  for  sulphur  in  coal, 
233 

Petroleum,    see   liquid   fuels,    gaso- 
line, kerosene,  etc. 


314 


SUBJECT  INDEX 


Phosphorus,  as  reagent  for  oxygen, 

30,  185 

Phosphorus  as  reagent  showing  ab- 
sence       of        unsaturated 
^    hydrocarbons,  29,  85 
precautions  in  handling,  30 
sometimes  inactive,  32 
Phosphorus  in  coal,  237 

standard    method    of    analysis, 

250 

Photometry,  see  candle  power 
Pintsch  gas,  29 
Pipettes  for  gas  analysis,   see   gas 

analysis 

Poisons  affecting  reaction  between 

oxygen  and  phosphorus,  32 

Portable    gas    analysis    apparatus, 

64-72 
Pressure  of  gases,  correction  for,  95, 

291,  292,  293 

Pressure  of  water  vapor,  table,  290 
Producer  gas,  analysis,  158 
efficiency  of  producer,  162 
formation,    156 
heating  value  of,  160 
sampling,  158 

interpretation  of  analysis,  159 
typical  analyses,  157 
volume  per  pound  of  carbon, 

161* 

Proximate  analysis  of  coal,  222 
Proximate  analysis  of   liquid  fuels, 

192 

Psychrometer,  113 
Pyrogallate,  as  reagent  for  oxygen, 
33,  86 

Quartz  combustion  tube  for  copper 
oxide,  57 

Quartz  combustion  tube  with  plati- 
num spiral,  51 

Radiation  corrections,  see  heating 
value  of  coal,  and  gas 

Record  form  for  gas  analysis,  61 
heating  value  of  coal,  271 
heating  value  of  gas,  105,  109 


Reduction     of      gas      volumes      to 
60°  and  30  in.  table,  292-4 
0°  and  760  mm.  dry,  table,  291 
Relative  humidity,  table,    295,  296 
Rubber  connections,   danger  of,   in 
gas  analysis,  18 

Sampling,  apparatus  for  gas,  1-13 
blast  furnace  gas,  141 
chimney  gases,  144 
crude     illuminating      gas     for 

naphthalene,  1 75 
coal,  see  coal  sampling 
coal,  standard  method  for 

laboratory  sampling,  240 
coke,  219 
standard  method  of  laboratory 

sampling,  257 
see  gas  sampling 
liquid  fuels,  187 
producer  gas,  158 
suspended  particles  in  gas,  140 
tubes  for  gases,  2 
Saturating  water  in  sampling  tubes, 

8 

Saturating  water  of  burette,  18 
Saturation  pressure  of  water  vapor, 

table,  290 
Saturating  water  in  gas  meter,  102, 

132 
Slate,    as    cause    of    error    in    coal 

sampling,  208 
separation  by  washing,  239 
Sodium  hydrosulphite,  as  reagent  for 

oxygen,  33 

Sodium  hydroxide,  reagent,  28 
Sodium  peroxide,  care  of,  285 
Solubility  of  gases  in  water,  6 
Specific     gravity     compared     with 
Baume"    scale    for    liquids 
lighter  than  water,  table, 
304 

Specific  gravity  of  gas,  determina- 
tion of,  181 

Specific  gravity  of  gases,  table,  301 
Specific  gravity  of  liquid  fuels,  deter- 
mination, 191 


SUBJECT  INDEX 


315 


Specific  heat  of  gases,  determination 

of,  150 
Specific  heats  of 

gases,  tables  303 

material  in  bomb  calorimeter, 

277 

Stack  gases,  see  chimney  gases 
Standard  method  of  coal  analysis, 

240 

coke  analysis,  257 
coal  sampling,  214 
coke  sampling,  216 
Standard    conditions    for    measure- 
ment of  gases,  76,  95 
Stopcocks,  care  of,  17 
Storage  of  gases,  11 
Sugar  as  standard  in  calorimetry,  278 
Sulphates  in  coal  ash,  230 
Sulphur,  analysis  of  in  coal,  232 
Atkinson  method,  233 
Parr's  photometric  method,  235 
Peroxide  method,  233 
in  washings  from  bomb  calori- 
meter, 235 
Sulphur,  corrections  for  oxidation  in 

bomb  calorimeter,  274 
total  in  illuminating  gas,  170 
Sulphur  dioxide,  removal  with  car- 
bon dioxide,  28,  84 
Sulphuretted  hydrogen,  see  hydro- 
gen sulphide 

Sulphuric  acid,  fuming  as  reagent,  29 
Suspended  particles  in  gas,  138 
Suspended  particles  in  gas,   distri- 
bution in  main,  138 
Suspended    particles   in   gas,    mean 

velocity,  139 
Suspended  particles  in  gas,  sampling, 

140 

Suspended  solids  in  liquid  fuels,  192 
Suspended  tar  in  gas,  estimation,  142 

Table  photometer,   121 
Tar  as  fuel,  see  liquid  fuel 
Tar  camera,  142 

Tar  particles  in  gas,  electrical  preci- 
pitation, 143 


Tar,  estimation  of  naphthalene  in, 

176 

moisture  in,  192 
Tar  suspended  in  gas,   estimation, 

142 
Temperature    of   gases,    corrections 

for,  95 
Temperature  of  initial  combustion  of 

various  gases,  56 

Temperature  measurement  in  calori- 
metry, errors  in,  108,  267, 

280 
Thermal  conductivity  as  method  of 

gas  analysis,  73 
Thermometers,  table  of  corrections 

for  emergent  stem,  299 

Ultimate  analysis  of  coal,  236 

standard  method,  251 
Unsaturated    hydrocarbons,    deter- 
mination of,  28,  85 

Variations  from  gas  laws,  90 

Volatile  matter  in  coal,  228 

standard  method  of  analysis, 
245 

Volume  of  gases,  formula  for  reduc- 
tion to  standard  con- 
dition, 76 

Volume  of  chimney  gas  per  pound  of 
coal,  148 

Volume  of  gases,  tables  for  reduction 
to  standard  conditions, 
291-4 

Volume  of  producer  gas  per  pound 
coal,  160 

Water,  combined  in  coal,  151 

saturated  with  air,  composition 
of  dissolved  gases,  7 
Water    value    of    calorimeter,    see 

heating  value  of  coal 
Water   vapor,      table  of  saturation 

pressure,  290 

Water  vapor,  table  of  specific  heats, 
303 


316  SUBJECT  INDEX 

Water  vapor,  volume  taken  up  by  Water,  weight  of  one  cubic  foot  at 
one      cu.    ft.      air,     table,  various  temperatures,  94 

304  Weathered  coal,  changes  in,  224,  262 

weight  percu.  ft.  of  saturated  air,  Wet  gas  meter,  see  gas  meter 

112  Wet  and  dry  bulb  thermometers,  113 

Water,  weight  of  one  liter  at  various  Wiring  rubber  connections,  19 

temperature,  265  Wiring  stopper  into  burette,  78 


INDEX  OF  AUTHORITIES  CITED 


Allen  and  Jacobs,  191 

Allen  and  Moyer,  67 

American  Chemical  Society,  see 
Committee  on  coal  analy- 
sis, 

American  Gas  Institute,  108,  111, 
136 

Anderson,  34,  184 

American  Society  for  Testing  Ma- 
terials, 193,  198,  214,  219, 
240,  257,  272 

Atkinson,  234 

Atwater,  259 

Atwater  and  Snell,  277 

Badger,  35,  227 

Bailey,  208 

Barker,  233 

Barkley  and  Flagg,  73 

Bartlett,  87 

Benton,  10 

Berthelot,  32,  258 

Blauvelt,  141 

Bleier,  79 

Brady,  141 

Brodhun,  129 

Bunsen,  129,  181 

Bunsen  and  Playfair,  74 

Bunte,  68,  167 

Bureau   of   Mines,    144,    157,    187, 

213,  214,  224,  243 
Bureau  of  Standards,  106,  108,  109, 

170,  182,  265,  297,  298 
Burrell,  185 

Burrell  and  Robertson,  184 
Burrell  and  Seibert,  73,  90,  185 

Campbell,  16,  38,  44,  56 
Cheney,  259 
Chollar,  70 
Church,  192 


Coleman  and  Smith,  174 
Committee   on    coal    analysis,    228, 

229,  239,  240,  280 
Coquillion,  51 
Cottrell,  143 

Davis,  see  Field  ner 
Davis  and  Davis,  167 
Davis  and  Fairchild,  239 
David  &  Wallace,  262 
Dennis,  52 

Dennis  and  Hopkins,  88 
Dennis  and  McCarthey,  166 
Dickinson,  272,  277,  280 
Doherty,  116 
Doyere,  74 
Drehschmidt,  170 
Dykema,  185 

Earnshaw,  85,  117 
Edwards,  73,  182 
Eschka,  232,  247 

Fairchild,  239 

Favre  and  Silverman,  283 

Fernald  and  Smith,  157 

Field,  232 

Fieldner  and  Davis,  228 

Fieldner,  Hall  and  Field,  232 

Fieldner  and  Selvig,  281 

Flagg,  73 

Franz en,  34 

Gas  Chemists  hand  book,  301,  302 

Gill,  44,  47 

Gill  and  Bartlett,  87 

Graefe,  116 

Haber  and  Oechelhauser,  167 

Hall,  232 

Harbeck  and  Lunge,  167 


317 


318 


AUTHOR  INDEX 


Harcourt,  126 

Harding,  170 

Hart,  38 

Hartmann,  39 

Hartley,  93 

Hefner,  121 

Herapel,  38,  39,  51,  53,  55,  75,  116, 

166,  258 
Henning,  150 

Hillebrand  and  Badger,  227 
Hinman,  47 
Heuse,  290 

Holborn  and  Henning,  150 
Holmes,  209 
Hopkins,  52,  88 
Hulett,  227 

Jacobs,  191 
Jaeger,  56 
Jenkins,  170 
Jones,  36 
Jesse,  280 
Junkers,  93 

Kinnicut  and  Sanford,  86 

Klumpp,  137 

Krauskopf,  37 

Kreisinger,  Augustine  and  Ovits,  144 

Kroeker,  236 

Kiister,  174 

Lavoisier,  74 
Le  Chatelier,  150 
Leeson,  129 
Lord,  239 
Lummer,  129 
Lunge,  167 

McBride,  Weaver  and  Edwards,  169 

McCarthy,  166 

McWhorter,  87 

Mack  and  Hulett,  227 

Mahler,  258 

Mallard,  150 

Morgan  and  McWhorter,  87 

Morton,  166 

Moyer,  67 

Mueller,  179 


National    Fire    Protection    Associa- 
tion, 202 
Nesmjelow,  55 
Nicloux,  86 
Noyes,  50 

Oechelhauser,  167 
Ovitz,  211 
Orsat,  35,  65 

Paal,  39 

Parr,   116,  228,  230,  233,  235,  236, 

238,  259,  283 
Pennock  and  Morton,  233 
Petterson,  77 
Pfaundler,  268 
Playfair,  181 
Pope,  214 
Porter,  225 
Porter  and  Ovitz,  211 
Purdy,  37 

Ramsburg,  169 

Regester,  235,  250 

Regnault  and  Reiset,  74 

Regnault         and         Pfaundler, 

268 

Reiset,  74 

Richards  and  Jesse,  188 
Robertson,  184 
Rolland,  64 
Rutten,  174 

Sanford,  86 

Scheel  and  Heuse,  290 

Scheurer-Kestner,  283 

Schilling,  181 

Schlosing  and  Rolland,  64 

Seibert,  73,  90,  185 

Selvig,  281 

Shepherd,  50 

Silverman,  283 

Small,  33 

Smith,  157 

Snell,  277 

Somermeier,  274 

Steere,  142 


AUTHOR  INDEX 


319 


Stevenson,  259 
Sundstrom,  233 

Thompson,  282 
Threlfall,  139 
Tutwiler,  170 

U.  S.  Fuel  Administration,  201 
United  Gas  Improvement  Co.,  301, 
302 


U.  S.  Geological  Survey,  289 
U.  S.  Weather  Bureau,  113 

Waidner  and  Mueller,  106 

Wallace,  262 

Weather  Bureau,  113 

Weaver,  73,  169 

White,  A.  H.,  16,  44,  53,  77,  88,  139, 

175 
White,  W.  P.,  280 


H 


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